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Editing File: /usr/share/nodejs/popper.js/dist/popper.js

var isBrowser = typeof window !== 'undefined' && typeof document !== 'undefined' && typeof navigator !== 'undefined';

var supportsMicroTasks = isBrowser && window.Promise;

/**
* Create a debounced version of a method, that's asynchronously deferred
* but called in the minimum time possible.
*
* @method
* @memberof Popper.Utils
* @argument {Function} fn
* @returns {Function}
*/
var debounce = (supportsMicroTasks
  ? microtaskDebounce
  : taskDebounce);

/**
 * Check if the given variable is a function
 * @method
 * @memberof Popper.Utils
 * @argument {Any} functionToCheck - variable to check
 * @returns {Boolean} answer to: is a function?
 */
function isFunction(functionToCheck) {
  var getType = {};
  return (
    functionToCheck &&
    getType.toString.call(functionToCheck) === '[object Function]'
  );
}

/**
 * Get CSS computed property of the given element
 * @method
 * @memberof Popper.Utils
 * @argument {Eement} element
 * @argument {String} property
 */
function getStyleComputedProperty(element, property) {
  if (element.nodeType !== 1) {
    return [];
  }
  // NOTE: 1 DOM access here
  var window = element.ownerDocument.defaultView;
  var css = window.getComputedStyle(element, null);
  return property ? css[property] : css;
}

/**
 * Returns the parentNode or the host of the element
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} parent
 */
function getParentNode(element) {
  if (element.nodeName === 'HTML') {
    return element;
  }
  return element.parentNode || element.host;
}

/**
 * Returns the scrolling parent of the given element
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} scroll parent
 */
function getScrollParent(element) {
  // Return body, `getScroll` will take care to get the correct `scrollTop` from it
  if (!element) {
    return document.body
  }

switch (element.nodeName) {
    case 'HTML':
    case 'BODY':
      return element.ownerDocument.body
    case '#document':
      return element.body
  }

// Firefox want us to check `-x` and `-y` variations as well
  var ref = getStyleComputedProperty(element);
  var overflow = ref.overflow;
  var overflowX = ref.overflowX;
  var overflowY = ref.overflowY;
  if (/(auto|scroll|overlay)/.test(overflow + overflowY + overflowX)) {
    return element;
  }

return getScrollParent(getParentNode(element));
}

/**
 * Returns the reference node of the reference object, or the reference object itself.
 * @method
 * @memberof Popper.Utils
 * @param {Element|Object} reference - the reference element (the popper will be relative to this)
 * @returns {Element} parent
 */
function getReferenceNode(reference) {
  return reference && reference.referenceNode ? reference.referenceNode : reference;
}

var isIE11 = isBrowser && !!(window.MSInputMethodContext && document.documentMode);
var isIE10 = isBrowser && /MSIE 10/.test(navigator.userAgent);

/**
 * Determines if the browser is Internet Explorer
 * @method
 * @memberof Popper.Utils
 * @param {Number} version to check
 * @returns {Boolean} isIE
 */
function isIE(version) {
  if (version === 11) {
    return isIE11;
  }
  if (version === 10) {
    return isIE10;
  }
  return isIE11 || isIE10;
}

/**
 * Returns the offset parent of the given element
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} offset parent
 */
function getOffsetParent(element) {
  if (!element) {
    return document.documentElement;
  }

var noOffsetParent = isIE(10) ? document.body : null;

// NOTE: 1 DOM access here
  var offsetParent = element.offsetParent || null;
  // Skip hidden elements which don't have an offsetParent
  while (offsetParent === noOffsetParent && element.nextElementSibling) {
    offsetParent = (element = element.nextElementSibling).offsetParent;
  }

var nodeName = offsetParent && offsetParent.nodeName;

if (!nodeName || nodeName === 'BODY' || nodeName === 'HTML') {
    return element ? element.ownerDocument.documentElement : document.documentElement;
  }

// .offsetParent will return the closest TH, TD or TABLE in case
  // no offsetParent is present, I hate this job...
  if (
    ['TH', 'TD', 'TABLE'].indexOf(offsetParent.nodeName) !== -1 &&
    getStyleComputedProperty(offsetParent, 'position') === 'static'
  ) {
    return getOffsetParent(offsetParent);
  }

return offsetParent;
}

function isOffsetContainer(element) {
  var nodeName = element.nodeName;
  if (nodeName === 'BODY') {
    return false;
  }
  return (
    nodeName === 'HTML' || getOffsetParent(element.firstElementChild) === element
  );
}

/**
 * Finds the root node (document, shadowDOM root) of the given element
 * @method
 * @memberof Popper.Utils
 * @argument {Element} node
 * @returns {Element} root node
 */
function getRoot(node) {
  if (node.parentNode !== null) {
    return getRoot(node.parentNode);
  }

return node;
}

/**
 * Finds the offset parent common to the two provided nodes
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element1
 * @argument {Element} element2
 * @returns {Element} common offset parent
 */
function findCommonOffsetParent(element1, element2) {
  // This check is needed to avoid errors in case one of the elements isn't defined for any reason
  if (!element1 || !element1.nodeType || !element2 || !element2.nodeType) {
    return document.documentElement;
  }

// Here we make sure to give as "start" the element that comes first in the DOM
  var order =
    element1.compareDocumentPosition(element2) &
    Node.DOCUMENT_POSITION_FOLLOWING;
  var start = order ? element1 : element2;
  var end = order ? element2 : element1;

// Get common ancestor container
  var range = document.createRange();
  range.setStart(start, 0);
  range.setEnd(end, 0);
  var commonAncestorContainer = range.commonAncestorContainer;

// Both nodes are inside #document
  if (
    (element1 !== commonAncestorContainer &&
      element2 !== commonAncestorContainer) ||
    start.contains(end)
  ) {
    if (isOffsetContainer(commonAncestorContainer)) {
      return commonAncestorContainer;
    }

return getOffsetParent(commonAncestorContainer);
  }

// one of the nodes is inside shadowDOM, find which one
  var element1root = getRoot(element1);
  if (element1root.host) {
    return findCommonOffsetParent(element1root.host, element2);
  } else {
    return findCommonOffsetParent(element1, getRoot(element2).host);
  }
}

/**
 * Gets the scroll value of the given element in the given side (top and left)
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @argument {String} side `top` or `left`
 * @returns {number} amount of scrolled pixels
 */
function getScroll(element, side) {
  if ( side === void 0 ) side = 'top';

var upperSide = side === 'top' ? 'scrollTop' : 'scrollLeft';
  var nodeName = element.nodeName;

if (nodeName === 'BODY' || nodeName === 'HTML') {
    var html = element.ownerDocument.documentElement;
    var scrollingElement = element.ownerDocument.scrollingElement || html;
    return scrollingElement[upperSide];
  }

return element[upperSide];
}

/*
 * Sum or subtract the element scroll values (left and top) from a given rect object
 * @method
 * @memberof Popper.Utils
 * @param {Object} rect - Rect object you want to change
 * @param {HTMLElement} element - The element from the function reads the scroll values
 * @param {Boolean} subtract - set to true if you want to subtract the scroll values
 * @return {Object} rect - The modifier rect object
 */
function includeScroll(rect, element, subtract) {
  if ( subtract === void 0 ) subtract = false;

var scrollTop = getScroll(element, 'top');
  var scrollLeft = getScroll(element, 'left');
  var modifier = subtract ? -1 : 1;
  rect.top += scrollTop * modifier;
  rect.bottom += scrollTop * modifier;
  rect.left += scrollLeft * modifier;
  rect.right += scrollLeft * modifier;
  return rect;
}

/*
 * Helper to detect borders of a given element
 * @method
 * @memberof Popper.Utils
 * @param {CSSStyleDeclaration} styles
 * Result of `getStyleComputedProperty` on the given element
 * @param {String} axis - `x` or `y`
 * @return {number} borders - The borders size of the given axis
 */

function getBordersSize(styles, axis) {
  var sideA = axis === 'x' ? 'Left' : 'Top';
  var sideB = sideA === 'Left' ? 'Right' : 'Bottom';

return (
    parseFloat(styles[("border" + sideA + "Width")]) +
    parseFloat(styles[("border" + sideB + "Width")])
  );
}

function getSize(axis, body, html, computedStyle) {
  return Math.max(
    body[("offset" + axis)],
    body[("scroll" + axis)],
    html[("client" + axis)],
    html[("offset" + axis)],
    html[("scroll" + axis)],
    isIE(10)
      ? (parseInt(html[("offset" + axis)]) + 
      parseInt(computedStyle[("margin" + (axis === 'Height' ? 'Top' : 'Left'))]) + 
      parseInt(computedStyle[("margin" + (axis === 'Height' ? 'Bottom' : 'Right'))]))
    : 0 
  );
}

function getWindowSizes(document) {
  var body = document.body;
  var html = document.documentElement;
  var computedStyle = isIE(10) && getComputedStyle(html);

return {
    height: getSize('Height', body, html, computedStyle),
    width: getSize('Width', body, html, computedStyle),
  };
}

/**
 * Given element offsets, generate an output similar to getBoundingClientRect
 * @method
 * @memberof Popper.Utils
 * @argument {Object} offsets
 * @returns {Object} ClientRect like output
 */
function getClientRect(offsets) {
  return Object.assign({}, offsets,
    {right: offsets.left + offsets.width,
    bottom: offsets.top + offsets.height});
}

/**
 * Get bounding client rect of given element
 * @method
 * @memberof Popper.Utils
 * @param {HTMLElement} element
 * @return {Object} client rect
 */
function getBoundingClientRect(element) {
  var rect = {};

// IE10 10 FIX: Please, don't ask, the element isn't
  // considered in DOM in some circumstances...
  // This isn't reproducible in IE10 compatibility mode of IE11
  try {
    if (isIE(10)) {
      rect = element.getBoundingClientRect();
      var scrollTop = getScroll(element, 'top');
      var scrollLeft = getScroll(element, 'left');
      rect.top += scrollTop;
      rect.left += scrollLeft;
      rect.bottom += scrollTop;
      rect.right += scrollLeft;
    }
    else {
      rect = element.getBoundingClientRect();
    }
  }
  catch(e){}

var result = {
    left: rect.left,
    top: rect.top,
    width: rect.right - rect.left,
    height: rect.bottom - rect.top,
  };

// subtract scrollbar size from sizes
  var sizes = element.nodeName === 'HTML' ? getWindowSizes(element.ownerDocument) : {};
  var width =
    sizes.width || element.clientWidth || result.width;
  var height =
    sizes.height || element.clientHeight || result.height;

var horizScrollbar = element.offsetWidth - width;
  var vertScrollbar = element.offsetHeight - height;

// if an hypothetical scrollbar is detected, we must be sure it's not a `border`
  // we make this check conditional for performance reasons
  if (horizScrollbar || vertScrollbar) {
    var styles = getStyleComputedProperty(element);
    horizScrollbar -= getBordersSize(styles, 'x');
    vertScrollbar -= getBordersSize(styles, 'y');

result.width -= horizScrollbar;
    result.height -= vertScrollbar;
  }

return getClientRect(result);
}

function getOffsetRectRelativeToArbitraryNode(children, parent, fixedPosition) {
  if ( fixedPosition === void 0 ) fixedPosition = false;

var isIE10 = isIE(10);
  var isHTML = parent.nodeName === 'HTML';
  var childrenRect = getBoundingClientRect(children);
  var parentRect = getBoundingClientRect(parent);
  var scrollParent = getScrollParent(children);

var styles = getStyleComputedProperty(parent);
  var borderTopWidth = parseFloat(styles.borderTopWidth);
  var borderLeftWidth = parseFloat(styles.borderLeftWidth);

// In cases where the parent is fixed, we must ignore negative scroll in offset calc
  if(fixedPosition && isHTML) {
    parentRect.top = Math.max(parentRect.top, 0);
    parentRect.left = Math.max(parentRect.left, 0);
  }
  var offsets = getClientRect({
    top: childrenRect.top - parentRect.top - borderTopWidth,
    left: childrenRect.left - parentRect.left - borderLeftWidth,
    width: childrenRect.width,
    height: childrenRect.height,
  });
  offsets.marginTop = 0;
  offsets.marginLeft = 0;

// Subtract margins of documentElement in case it's being used as parent
  // we do this only on HTML because it's the only element that behaves
  // differently when margins are applied to it. The margins are included in
  // the box of the documentElement, in the other cases not.
  if (!isIE10 && isHTML) {
    var marginTop = parseFloat(styles.marginTop);
    var marginLeft = parseFloat(styles.marginLeft);

offsets.top -= borderTopWidth - marginTop;
    offsets.bottom -= borderTopWidth - marginTop;
    offsets.left -= borderLeftWidth - marginLeft;
    offsets.right -= borderLeftWidth - marginLeft;

// Attach marginTop and marginLeft because in some circumstances we may need them
    offsets.marginTop = marginTop;
    offsets.marginLeft = marginLeft;
  }

if (
    isIE10 && !fixedPosition
      ? parent.contains(scrollParent)
      : parent === scrollParent && scrollParent.nodeName !== 'BODY'
  ) {
    offsets = includeScroll(offsets, parent);
  }

return offsets;
}

function getViewportOffsetRectRelativeToArtbitraryNode(element, excludeScroll) {
  if ( excludeScroll === void 0 ) excludeScroll = false;

var html = element.ownerDocument.documentElement;
  var relativeOffset = getOffsetRectRelativeToArbitraryNode(element, html);
  var width = Math.max(html.clientWidth, window.innerWidth || 0);
  var height = Math.max(html.clientHeight, window.innerHeight || 0);

var scrollTop = !excludeScroll ? getScroll(html) : 0;
  var scrollLeft = !excludeScroll ? getScroll(html, 'left') : 0;

var offset = {
    top: scrollTop - relativeOffset.top + relativeOffset.marginTop,
    left: scrollLeft - relativeOffset.left + relativeOffset.marginLeft,
    width: width,
    height: height,
  };

return getClientRect(offset);
}

/**
 * Check if the given element is fixed or is inside a fixed parent
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @argument {Element} customContainer
 * @returns {Boolean} answer to "isFixed?"
 */
function isFixed(element) {
  var nodeName = element.nodeName;
  if (nodeName === 'BODY' || nodeName === 'HTML') {
    return false;
  }
  if (getStyleComputedProperty(element, 'position') === 'fixed') {
    return true;
  }
  var parentNode = getParentNode(element);
  if (!parentNode) {
    return false;
  }
  return isFixed(parentNode);
}

/**
 * Finds the first parent of an element that has a transformed property defined
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} first transformed parent or documentElement
 */

function getFixedPositionOffsetParent(element) {
  // This check is needed to avoid errors in case one of the elements isn't defined for any reason
   if (!element || !element.parentElement || isIE()) {
    return document.documentElement;
  }
  var el = element.parentElement;
  while (el && getStyleComputedProperty(el, 'transform') === 'none') {
    el = el.parentElement;
  }
  return el || document.documentElement;

}

/**
 * Computed the boundaries limits and return them
 * @method
 * @memberof Popper.Utils
 * @param {HTMLElement} popper
 * @param {HTMLElement} reference
 * @param {number} padding
 * @param {HTMLElement} boundariesElement - Element used to define the boundaries
 * @param {Boolean} fixedPosition - Is in fixed position mode
 * @returns {Object} Coordinates of the boundaries
 */
function getBoundaries(
  popper,
  reference,
  padding,
  boundariesElement,
  fixedPosition
) {
  if ( fixedPosition === void 0 ) fixedPosition = false;

// NOTE: 1 DOM access here

var boundaries = { top: 0, left: 0 };
  var offsetParent = fixedPosition ? getFixedPositionOffsetParent(popper) : findCommonOffsetParent(popper, getReferenceNode(reference));

// Handle viewport case
  if (boundariesElement === 'viewport' ) {
    boundaries = getViewportOffsetRectRelativeToArtbitraryNode(offsetParent, fixedPosition);
  }

else {
    // Handle other cases based on DOM element used as boundaries
    var boundariesNode;
    if (boundariesElement === 'scrollParent') {
      boundariesNode = getScrollParent(getParentNode(reference));
      if (boundariesNode.nodeName === 'BODY') {
        boundariesNode = popper.ownerDocument.documentElement;
      }
    } else if (boundariesElement === 'window') {
      boundariesNode = popper.ownerDocument.documentElement;
    } else {
      boundariesNode = boundariesElement;
    }

var offsets = getOffsetRectRelativeToArbitraryNode(
      boundariesNode,
      offsetParent,
      fixedPosition
    );

// In case of HTML, we need a different computation
    if (boundariesNode.nodeName === 'HTML' && !isFixed(offsetParent)) {
      var ref = getWindowSizes(popper.ownerDocument);
      var height = ref.height;
      var width = ref.width;
      boundaries.top += offsets.top - offsets.marginTop;
      boundaries.bottom = height + offsets.top;
      boundaries.left += offsets.left - offsets.marginLeft;
      boundaries.right = width + offsets.left;
    } else {
      // for all the other DOM elements, this one is good
      boundaries = offsets;
    }
  }

// Add paddings
  padding = padding || 0;
  var isPaddingNumber = typeof padding === 'number';
  boundaries.left += isPaddingNumber ? padding : padding.left || 0; 
  boundaries.top += isPaddingNumber ? padding : padding.top || 0; 
  boundaries.right -= isPaddingNumber ? padding : padding.right || 0; 
  boundaries.bottom -= isPaddingNumber ? padding : padding.bottom || 0;

return boundaries;
}

function getArea(ref) {
  var width = ref.width;
  var height = ref.height;

return width * height;
}

/**
 * Utility used to transform the `auto` placement to the placement with more
 * available space.
 * @method
 * @memberof Popper.Utils
 * @argument {Object} data - The data object generated by update method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function computeAutoPlacement(
  placement,
  refRect,
  popper,
  reference,
  boundariesElement,
  padding
) {
  if ( padding === void 0 ) padding = 0;

if (placement.indexOf('auto') === -1) {
    return placement;
  }

var boundaries = getBoundaries(
    popper,
    reference,
    padding,
    boundariesElement
  );

var rects = {
    top: {
      width: boundaries.width,
      height: refRect.top - boundaries.top,
    },
    right: {
      width: boundaries.right - refRect.right,
      height: boundaries.height,
    },
    bottom: {
      width: boundaries.width,
      height: boundaries.bottom - refRect.bottom,
    },
    left: {
      width: refRect.left - boundaries.left,
      height: boundaries.height,
    },
  };

var filteredAreas = sortedAreas.filter(
    function (ref) {
        var width = ref.width;
        var height = ref.height;

return width >= popper.clientWidth && height >= popper.clientHeight;
  }
  );

var computedPlacement = filteredAreas.length > 0
    ? filteredAreas[0].key
    : sortedAreas[0].key;

var variation = placement.split('-')[1];

return computedPlacement + (variation ? ("-" + variation) : '');
}

/**
 * Get offsets to the reference element
 * @method
 * @memberof Popper.Utils
 * @param {Object} state
 * @param {Element} popper - the popper element
 * @param {Element} reference - the reference element (the popper will be relative to this)
 * @param {Element} fixedPosition - is in fixed position mode
 * @returns {Object} An object containing the offsets which will be applied to the popper
 */
function getReferenceOffsets(state, popper, reference, fixedPosition) {
  if ( fixedPosition === void 0 ) fixedPosition = null;

var commonOffsetParent = fixedPosition ? getFixedPositionOffsetParent(popper) : findCommonOffsetParent(popper, getReferenceNode(reference));
  return getOffsetRectRelativeToArbitraryNode(reference, commonOffsetParent, fixedPosition);
}

/**
 * Get the outer sizes of the given element (offset size + margins)
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Object} object containing width and height properties
 */
function getOuterSizes(element) {
  var window = element.ownerDocument.defaultView;
  var styles = window.getComputedStyle(element);
  var x = parseFloat(styles.marginTop || 0) + parseFloat(styles.marginBottom || 0);
  var y = parseFloat(styles.marginLeft || 0) + parseFloat(styles.marginRight || 0);
  var result = {
    width: element.offsetWidth + y,
    height: element.offsetHeight + x,
  };
  return result;
}

/**
 * Get the opposite placement of the given one
 * @method
 * @memberof Popper.Utils
 * @argument {String} placement
 * @returns {String} flipped placement
 */
function getOppositePlacement(placement) {
  var hash = { left: 'right', right: 'left', bottom: 'top', top: 'bottom' };
  return placement.replace(/left|right|bottom|top/g, function (matched) { return hash[matched]; });
}

/**
 * Get offsets to the popper
 * @method
 * @memberof Popper.Utils
 * @param {Object} position - CSS position the Popper will get applied
 * @param {HTMLElement} popper - the popper element
 * @param {Object} referenceOffsets - the reference offsets (the popper will be relative to this)
 * @param {String} placement - one of the valid placement options
 * @returns {Object} popperOffsets - An object containing the offsets which will be applied to the popper
 */
function getPopperOffsets(popper, referenceOffsets, placement) {
  placement = placement.split('-')[0];

// Get popper node sizes
  var popperRect = getOuterSizes(popper);

// Add position, width and height to our offsets object
  var popperOffsets = {
    width: popperRect.width,
    height: popperRect.height,
  };

// depending by the popper placement we have to compute its offsets slightly differently
  var isHoriz = ['right', 'left'].indexOf(placement) !== -1;
  var mainSide = isHoriz ? 'top' : 'left';
  var secondarySide = isHoriz ? 'left' : 'top';
  var measurement = isHoriz ? 'height' : 'width';
  var secondaryMeasurement = !isHoriz ? 'height' : 'width';

popperOffsets[mainSide] =
    referenceOffsets[mainSide] +
    referenceOffsets[measurement] / 2 -
    popperRect[measurement] / 2;
  if (placement === secondarySide) {
    popperOffsets[secondarySide] =
      referenceOffsets[secondarySide] - popperRect[secondaryMeasurement];
  } else {
    popperOffsets[secondarySide] =
      referenceOffsets[getOppositePlacement(secondarySide)];
  }

return popperOffsets;
}

/**
 * Mimics the `find` method of Array
 * @method
 * @memberof Popper.Utils
 * @argument {Array} arr
 * @argument prop
 * @argument value
 * @returns index or -1
 */
function find(arr, check) {
  // use native find if supported
  if (Array.prototype.find) {
    return arr.find(check);
  }

// use `filter` to obtain the same behavior of `find`
  return arr.filter(check)[0];
}

/**
 * Return the index of the matching object
 * @method
 * @memberof Popper.Utils
 * @argument {Array} arr
 * @argument prop
 * @argument value
 * @returns index or -1
 */
function findIndex(arr, prop, value) {
  // use native findIndex if supported
  if (Array.prototype.findIndex) {
    return arr.findIndex(function (cur) { return cur[prop] === value; });
  }

// use `find` + `indexOf` if `findIndex` isn't supported
  var match = find(arr, function (obj) { return obj[prop] === value; });
  return arr.indexOf(match);
}

/**
 * Loop trough the list of modifiers and run them in order,
 * each of them will then edit the data object.
 * @method
 * @memberof Popper.Utils
 * @param {dataObject} data
 * @param {Array} modifiers
 * @param {String} ends - Optional modifier name used as stopper
 * @returns {dataObject}
 */
function runModifiers(modifiers, data, ends) {
  var modifiersToRun = ends === undefined
    ? modifiers
    : modifiers.slice(0, findIndex(modifiers, 'name', ends));

modifiersToRun.forEach(function (modifier) {
    if (modifier['function']) { // eslint-disable-line dot-notation
      console.warn('`modifier.function` is deprecated, use `modifier.fn`!');
    }
    var fn = modifier['function'] || modifier.fn; // eslint-disable-line dot-notation
    if (modifier.enabled && isFunction(fn)) {
      // Add properties to offsets to make them a complete clientRect object
      // we do this before each modifier to make sure the previous one doesn't
      // mess with these values
      data.offsets.popper = getClientRect(data.offsets.popper);
      data.offsets.reference = getClientRect(data.offsets.reference);

data = fn(data, modifier);
    }
  });

return data;
}

/**
 * Updates the position of the popper, computing the new offsets and applying
 * the new style. 
 * Prefer `scheduleUpdate` over `update` because of performance reasons.
 * @method
 * @memberof Popper
 */
function update() {
 // if popper is destroyed, don't perform any further update
 if (this.state.isDestroyed) {
 return;
 }

var data = {
    instance: this,
    styles: {},
    arrowStyles: {},
    attributes: {},
    flipped: false,
    offsets: {},
  };

// compute reference element offsets
  data.offsets.reference = getReferenceOffsets(
    this.state,
    this.popper,
    this.reference,
    this.options.positionFixed
  );

// compute auto placement, store placement inside the data object,
  // modifiers will be able to edit `placement` if needed
  // and refer to originalPlacement to know the original value
  data.placement = computeAutoPlacement(
    this.options.placement,
    data.offsets.reference,
    this.popper,
    this.reference,
    this.options.modifiers.flip.boundariesElement,
    this.options.modifiers.flip.padding
  );

// store the computed placement inside `originalPlacement`
  data.originalPlacement = data.placement;

data.positionFixed = this.options.positionFixed;

// compute the popper offsets
  data.offsets.popper = getPopperOffsets(
    this.popper,
    data.offsets.reference,
    data.placement
  );

data.offsets.popper.position = this.options.positionFixed
    ? 'fixed'
    : 'absolute';

// run the modifiers
  data = runModifiers(this.modifiers, data);

// the first `update` will call `onCreate` callback
  // the other ones will call `onUpdate` callback
  if (!this.state.isCreated) {
    this.state.isCreated = true;
    this.options.onCreate(data);
  } else {
    this.options.onUpdate(data);
  }
}

/**
 * Helper used to know if the given modifier is enabled.
 * @method
 * @memberof Popper.Utils
 * @returns {Boolean}
 */
function isModifierEnabled(modifiers, modifierName) {
  return modifiers.some(
    function (ref) {
      var name = ref.name;
      var enabled = ref.enabled;

return enabled && name === modifierName;
  }
  );
}

/**
 * Get the prefixed supported property name
 * @method
 * @memberof Popper.Utils
 * @argument {String} property (camelCase)
 * @returns {String} prefixed property (camelCase or PascalCase, depending on the vendor prefix)
 */
function getSupportedPropertyName(property) {
  var prefixes = [false, 'ms', 'Webkit', 'Moz', 'O'];
  var upperProp = property.charAt(0).toUpperCase() + property.slice(1);

for (var i = 0; i < prefixes.length; i++) {
 var prefix = prefixes[i];
 var toCheck = prefix ? ("" + prefix + upperProp) : property;
 if (typeof document.body.style[toCheck] !== 'undefined') {
 return toCheck;
 }
 }
 return null;
}

/**
 * Destroys the popper.
 * @method
 * @memberof Popper
 */
function destroy() {
  this.state.isDestroyed = true;

// touch DOM only if `applyStyle` modifier is enabled
  if (isModifierEnabled(this.modifiers, 'applyStyle')) {
    this.popper.removeAttribute('x-placement');
    this.popper.style.position = '';
    this.popper.style.top = '';
    this.popper.style.left = '';
    this.popper.style.right = '';
    this.popper.style.bottom = '';
    this.popper.style.willChange = '';
    this.popper.style[getSupportedPropertyName('transform')] = '';
  }

this.disableEventListeners();

// remove the popper if user explicitly asked for the deletion on destroy
  // do not use `remove` because IE11 doesn't support it
  if (this.options.removeOnDestroy) {
    this.popper.parentNode.removeChild(this.popper);
  }
  return this;
}

/**
 * Get the window associated with the element
 * @argument {Element} element
 * @returns {Window}
 */
function getWindow(element) {
  var ownerDocument = element.ownerDocument;
  return ownerDocument ? ownerDocument.defaultView : window;
}

function attachToScrollParents(scrollParent, event, callback, scrollParents) {
  var isBody = scrollParent.nodeName === 'BODY';
  var target = isBody ? scrollParent.ownerDocument.defaultView : scrollParent;
  target.addEventListener(event, callback, { passive: true });

if (!isBody) {
    attachToScrollParents(
      getScrollParent(target.parentNode),
      event,
      callback,
      scrollParents
    );
  }
  scrollParents.push(target);
}

/**
 * Setup needed event listeners used to update the popper position
 * @method
 * @memberof Popper.Utils
 * @private
 */
function setupEventListeners(
  reference,
  options,
  state,
  updateBound
) {
  // Resize event listener on window
  state.updateBound = updateBound;
  getWindow(reference).addEventListener('resize', state.updateBound, { passive: true });

// Scroll event listener on scroll parents
  var scrollElement = getScrollParent(reference);
  attachToScrollParents(
    scrollElement,
    'scroll',
    state.updateBound,
    state.scrollParents
  );
  state.scrollElement = scrollElement;
  state.eventsEnabled = true;

return state;
}

/**
 * It will add resize/scroll events and start recalculating
 * position of the popper element when they are triggered.
 * @method
 * @memberof Popper
 */
function enableEventListeners() {
  if (!this.state.eventsEnabled) {
    this.state = setupEventListeners(
      this.reference,
      this.options,
      this.state,
      this.scheduleUpdate
    );
  }
}

/**
 * Remove event listeners used to update the popper position
 * @method
 * @memberof Popper.Utils
 * @private
 */
function removeEventListeners(reference, state) {
  // Remove resize event listener on window
  getWindow(reference).removeEventListener('resize', state.updateBound);

// Remove scroll event listener on scroll parents
  state.scrollParents.forEach(function (target) {
    target.removeEventListener('scroll', state.updateBound);
  });

// Reset state
  state.updateBound = null;
  state.scrollParents = [];
  state.scrollElement = null;
  state.eventsEnabled = false;
  return state;
}

/**
 * It will remove resize/scroll events and won't recalculate popper position
 * when they are triggered. It also won't trigger `onUpdate` callback anymore,
 * unless you call `update` method manually.
 * @method
 * @memberof Popper
 */
function disableEventListeners() {
  if (this.state.eventsEnabled) {
    cancelAnimationFrame(this.scheduleUpdate);
    this.state = removeEventListeners(this.reference, this.state);
  }
}

/**
 * Tells if a given input is a number
 * @method
 * @memberof Popper.Utils
 * @param {*} input to check
 * @return {Boolean}
 */
function isNumeric(n) {
  return n !== '' && !isNaN(parseFloat(n)) && isFinite(n);
}

/**
 * Set the style to the given popper
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element - Element to apply the style to
 * @argument {Object} styles
 * Object with a list of properties and values which will be applied to the element
 */
function setStyles(element, styles) {
  Object.keys(styles).forEach(function (prop) {
    var unit = '';
    // add unit if the value is numeric and is one of the following
    if (
      ['width', 'height', 'top', 'right', 'bottom', 'left'].indexOf(prop) !==
        -1 &&
      isNumeric(styles[prop])
    ) {
      unit = 'px';
    }
    element.style[prop] = styles[prop] + unit;
  });
}

/**
 * Set the attributes to the given popper
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element - Element to apply the attributes to
 * @argument {Object} styles
 * Object with a list of properties and values which will be applied to the element
 */
function setAttributes(element, attributes) {
  Object.keys(attributes).forEach(function(prop) {
    var value = attributes[prop];
    if (value !== false) {
      element.setAttribute(prop, attributes[prop]);
    } else {
      element.removeAttribute(prop);
    }
  });
}

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @argument {Object} data.styles - List of style properties - values to apply to popper element
 * @argument {Object} data.attributes - List of attribute properties - values to apply to popper element
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The same data object
 */
function applyStyle(data) {
  // any property present in `data.styles` will be applied to the popper,
  // in this way we can make the 3rd party modifiers add custom styles to it
  // Be aware, modifiers could override the properties defined in the previous
  // lines of this modifier!
  setStyles(data.instance.popper, data.styles);

// any property present in `data.attributes` will be applied to the popper,
  // they will be set as HTML attributes of the element
  setAttributes(data.instance.popper, data.attributes);

// if arrowElement is defined and arrowStyles has some properties
  if (data.arrowElement && Object.keys(data.arrowStyles).length) {
    setStyles(data.arrowElement, data.arrowStyles);
  }

return data;
}

/**
 * Set the x-placement attribute before everything else because it could be used
 * to add margins to the popper margins needs to be calculated to get the
 * correct popper offsets.
 * @method
 * @memberof Popper.modifiers
 * @param {HTMLElement} reference - The reference element used to position the popper
 * @param {HTMLElement} popper - The HTML element used as popper
 * @param {Object} options - Popper.js options
 */
function applyStyleOnLoad(
  reference,
  popper,
  options,
  modifierOptions,
  state
) {
  // compute reference element offsets
  var referenceOffsets = getReferenceOffsets(state, popper, reference, options.positionFixed);

// compute auto placement, store placement inside the data object,
  // modifiers will be able to edit `placement` if needed
  // and refer to originalPlacement to know the original value
  var placement = computeAutoPlacement(
    options.placement,
    referenceOffsets,
    popper,
    reference,
    options.modifiers.flip.boundariesElement,
    options.modifiers.flip.padding
  );

popper.setAttribute('x-placement', placement);

// Apply `position` to popper before anything else because
  // without the position applied we can't guarantee correct computations
  setStyles(popper, { position: options.positionFixed ? 'fixed' : 'absolute' });

return options;
}

/**
 * @function
 * @memberof Popper.Utils
 * @argument {Object} data - The data object generated by `update` method
 * @argument {Boolean} shouldRound - If the offsets should be rounded at all
 * @returns {Object} The popper's position offsets rounded
 *
 * The tale of pixel-perfect positioning. It's still not 100% perfect, but as
 * good as it can be within reason.
 * Discussion here: https://github.com/FezVrasta/popper.js/pull/715
 *
 * Low DPI screens cause a popper to be blurry if not using full pixels (Safari
 * as well on High DPI screens).
 *
 * Firefox prefers no rounding for positioning and does not have blurriness on
 * high DPI screens.
 *
 * Only horizontal placement and left/right values need to be considered.
 */
function getRoundedOffsets(data, shouldRound) {
  var ref = data.offsets;
  var popper = ref.popper;
  var reference = ref.reference;
  var round = Math.round;
  var floor = Math.floor;
  var noRound = function (v) { return v; };
  
  var referenceWidth = round(reference.width);
  var popperWidth = round(popper.width);
  
  var isVertical = ['left', 'right'].indexOf(data.placement) !== -1;
  var isVariation = data.placement.indexOf('-') !== -1;
  var sameWidthParity = referenceWidth % 2 === popperWidth % 2;
  var bothOddWidth = referenceWidth % 2 === 1 && popperWidth % 2 === 1;

var horizontalToInteger = !shouldRound
    ? noRound
    : isVertical || isVariation || sameWidthParity
    ? round
    : floor;
  var verticalToInteger = !shouldRound ? noRound : round;

return {
    left: horizontalToInteger(
      bothOddWidth && !isVariation && shouldRound
        ? popper.left - 1
        : popper.left
    ),
    top: verticalToInteger(popper.top),
    bottom: verticalToInteger(popper.bottom),
    right: horizontalToInteger(popper.right),
  };
}

var isFirefox = isBrowser && /Firefox/i.test(navigator.userAgent);

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function computeStyle(data, options) {
  var x = options.x;
  var y = options.y;
  var ref = data.offsets;
  var popper = ref.popper;

// Remove this legacy support in Popper.js v2
  var legacyGpuAccelerationOption = find(
    data.instance.modifiers,
    function (modifier) { return modifier.name === 'applyStyle'; }
  ).gpuAcceleration;
  if (legacyGpuAccelerationOption !== undefined) {
    console.warn(
      'WARNING: `gpuAcceleration` option moved to `computeStyle` modifier and will not be supported in future versions of Popper.js!'
    );
  }
  var gpuAcceleration =
    legacyGpuAccelerationOption !== undefined
      ? legacyGpuAccelerationOption
      : options.gpuAcceleration;

var offsetParent = getOffsetParent(data.instance.popper);
  var offsetParentRect = getBoundingClientRect(offsetParent);

// Styles
  var styles = {
    position: popper.position,
  };

var offsets = getRoundedOffsets(
 data,
 window.devicePixelRatio < 2 || !isFirefox
 );

var sideA = x === 'bottom' ? 'top' : 'bottom';
  var sideB = y === 'right' ? 'left' : 'right';

// if gpuAcceleration is set to `true` and transform is supported,
  //  we use `translate3d` to apply the position to the popper we
  // automatically use the supported prefixed version if needed
  var prefixedProperty = getSupportedPropertyName('transform');

// now, let's make a step back and look at this code closely (wtf?)
 // If the content of the popper grows once it's been positioned, it
 // may happen that the popper gets misplaced because of the new content
 // overflowing its reference element
 // To avoid this problem, we provide two options (x and y), which allow
 // the consumer to define the offset origin.
 // If we position a popper on top of a reference element, we can set
 // `x` to `top` to make the popper grow towards its top instead of
 // its bottom.
 var left, top;
 if (sideA === 'bottom') {
 // when offsetParent is <html> the positioning is relative to the bottom of the screen (excluding the scrollbar)
 // and not the bottom of the html element
 if (offsetParent.nodeName === 'HTML') {
 top = -offsetParent.clientHeight + offsets.bottom;
 } else {
 top = -offsetParentRect.height + offsets.bottom;
 }
 } else {
 top = offsets.top;
 }
 if (sideB === 'right') {
 if (offsetParent.nodeName === 'HTML') {
 left = -offsetParent.clientWidth + offsets.right;
 } else {
 left = -offsetParentRect.width + offsets.right;
 }
 } else {
 left = offsets.left;
 }
 if (gpuAcceleration && prefixedProperty) {
 styles[prefixedProperty] = "translate3d(" + left + "px, " + top + "px, 0)";
 styles[sideA] = 0;
 styles[sideB] = 0;
 styles.willChange = 'transform';
 } else {
 // othwerise, we use the standard `top`, `left`, `bottom` and `right` properties
 var invertTop = sideA === 'bottom' ? -1 : 1;
 var invertLeft = sideB === 'right' ? -1 : 1;
 styles[sideA] = top * invertTop;
 styles[sideB] = left * invertLeft;
 styles.willChange = sideA + ", " + sideB;
 }

// Attributes
  var attributes = {
    'x-placement': data.placement,
  };

// Update `data` attributes, styles and arrowStyles
  data.attributes = Object.assign({}, attributes, data.attributes);
  data.styles = Object.assign({}, styles, data.styles);
  data.arrowStyles = Object.assign({}, data.offsets.arrow, data.arrowStyles);

return data;
}

/**
 * Helper used to know if the given modifier depends from another one. 
 * It checks if the needed modifier is listed and enabled.
 * @method
 * @memberof Popper.Utils
 * @param {Array} modifiers - list of modifiers
 * @param {String} requestingName - name of requesting modifier
 * @param {String} requestedName - name of requested modifier
 * @returns {Boolean}
 */
function isModifierRequired(
 modifiers,
 requestingName,
 requestedName
) {
 var requesting = find(modifiers, function (ref) {
 var name = ref.name;

return name === requestingName;
  });

var isRequired =
 !!requesting &&
 modifiers.some(function (modifier) {
 return (
 modifier.name === requestedName &&
 modifier.enabled &&
 modifier.order < requesting.order
 );
 });

if (!isRequired) {
    var requesting$1 = "`" + requestingName + "`";
    var requested = "`" + requestedName + "`";
    console.warn(
      (requested + " modifier is required by " + requesting$1 + " modifier in order to work, be sure to include it before " + requesting$1 + "!")
    );
  }
  return isRequired;
}

// arrow depends on keepTogether in order to work
  if (!isModifierRequired(data.instance.modifiers, 'arrow', 'keepTogether')) {
    return data;
  }

var arrowElement = options.element;

// if arrowElement is a string, suppose it's a CSS selector
  if (typeof arrowElement === 'string') {
    arrowElement = data.instance.popper.querySelector(arrowElement);

// if arrowElement is not found, don't run the modifier
    if (!arrowElement) {
      return data;
    }
  } else {
    // if the arrowElement isn't a query selector we must check that the
    // provided DOM node is child of its popper node
    if (!data.instance.popper.contains(arrowElement)) {
      console.warn(
        'WARNING: `arrow.element` must be child of its popper element!'
      );
      return data;
    }
  }

var placement = data.placement.split('-')[0];
  var ref = data.offsets;
  var popper = ref.popper;
  var reference = ref.reference;
  var isVertical = ['left', 'right'].indexOf(placement) !== -1;

var len = isVertical ? 'height' : 'width';
  var sideCapitalized = isVertical ? 'Top' : 'Left';
  var side = sideCapitalized.toLowerCase();
  var altSide = isVertical ? 'left' : 'top';
  var opSide = isVertical ? 'bottom' : 'right';
  var arrowElementSize = getOuterSizes(arrowElement)[len];

//
  // extends keepTogether behavior making sure the popper and its
  // reference have enough pixels in conjunction
  //

// top/left side
 if (reference[opSide] - arrowElementSize < popper[side]) {
 data.offsets.popper[side] -=
 popper[side] - (reference[opSide] - arrowElementSize);
 }
 // bottom/right side
 if (reference[side] + arrowElementSize > popper[opSide]) {
 data.offsets.popper[side] +=
 reference[side] + arrowElementSize - popper[opSide];
 }
 data.offsets.popper = getClientRect(data.offsets.popper);

// compute center of the popper
  var center = reference[side] + reference[len] / 2 - arrowElementSize / 2;

// Compute the sideValue using the updated popper offsets
  // take popper margin in account because we don't have this info available
  var css = getStyleComputedProperty(data.instance.popper);
  var popperMarginSide = parseFloat(css[("margin" + sideCapitalized)]);
  var popperBorderSide = parseFloat(css[("border" + sideCapitalized + "Width")]);
  var sideValue =
    center - data.offsets.popper[side] - popperMarginSide - popperBorderSide;

// prevent arrowElement from being placed not contiguously to its popper
  sideValue = Math.max(Math.min(popper[len] - arrowElementSize, sideValue), 0);

data.arrowElement = arrowElement;
  data.offsets.arrow = ( obj = {}, obj[side] = Math.round(sideValue), obj[altSide] = '', obj );

return data;
}

/**
 * Get the opposite placement variation of the given one
 * @method
 * @memberof Popper.Utils
 * @argument {String} placement variation
 * @returns {String} flipped placement variation
 */
function getOppositeVariation(variation) {
  if (variation === 'end') {
    return 'start';
  } else if (variation === 'start') {
    return 'end';
  }
  return variation;
}

/**
 * List of accepted placements to use as values of the `placement` option. 
 * Valid placements are:
 * - `auto`
 * - `top`
 * - `right`
 * - `bottom`
 * - `left`
 *
 * Each placement can have a variation from this list:
 * - `-start`
 * - `-end`
 *
 * Variations are interpreted easily if you think of them as the left to right
 * written languages. Horizontally (`top` and `bottom`), `start` is left and `end`
 * is right. 
 * Vertically (`left` and `right`), `start` is top and `end` is bottom.
 *
 * Some valid examples are:
 * - `top-end` (on top of reference, right aligned)
 * - `right-start` (on right of reference, top aligned)
 * - `bottom` (on bottom, centered)
 * - `auto-end` (on the side with more space available, alignment depends by placement)
 *
 * @static
 * @type {Array}
 * @enum {String}
 * @readonly
 * @method placements
 * @memberof Popper
 */
var placements = [
 'auto-start',
 'auto',
 'auto-end',
 'top-start',
 'top',
 'top-end',
 'right-start',
 'right',
 'right-end',
 'bottom-end',
 'bottom',
 'bottom-start',
 'left-end',
 'left',
 'left-start' ];

// Get rid of `auto` `auto-start` and `auto-end`
var validPlacements = placements.slice(3);

/**
 * Given an initial placement, returns all the subsequent placements
 * clockwise (or counter-clockwise).
 *
 * @method
 * @memberof Popper.Utils
 * @argument {String} placement - A valid placement (it accepts variations)
 * @argument {Boolean} counter - Set to true to walk the placements counterclockwise
 * @returns {Array} placements including their variations
 */
function clockwise(placement, counter) {
  if ( counter === void 0 ) counter = false;

var index = validPlacements.indexOf(placement);
  var arr = validPlacements
    .slice(index + 1)
    .concat(validPlacements.slice(0, index));
  return counter ? arr.reverse() : arr;
}

var BEHAVIORS = {
  FLIP: 'flip',
  CLOCKWISE: 'clockwise',
  COUNTERCLOCKWISE: 'counterclockwise',
};

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by update method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function flip(data, options) {
  // if `inner` modifier is enabled, we can't use the `flip` modifier
  if (isModifierEnabled(data.instance.modifiers, 'inner')) {
    return data;
  }

if (data.flipped && data.placement === data.originalPlacement) {
    // seems like flip is trying to loop, probably there's not enough space on any of the flippable sides
    return data;
  }

var boundaries = getBoundaries(
    data.instance.popper,
    data.instance.reference,
    options.padding,
    options.boundariesElement,
    data.positionFixed
  );

var placement = data.placement.split('-')[0];
  var placementOpposite = getOppositePlacement(placement);
  var variation = data.placement.split('-')[1] || '';

var flipOrder = [];

switch (options.behavior) {
    case BEHAVIORS.FLIP:
      flipOrder = [placement, placementOpposite];
      break;
    case BEHAVIORS.CLOCKWISE:
      flipOrder = clockwise(placement);
      break;
    case BEHAVIORS.COUNTERCLOCKWISE:
      flipOrder = clockwise(placement, true);
      break;
    default:
      flipOrder = options.behavior;
  }

flipOrder.forEach(function (step, index) {
    if (placement !== step || flipOrder.length === index + 1) {
      return data;
    }

placement = data.placement.split('-')[0];
    placementOpposite = getOppositePlacement(placement);

var popperOffsets = data.offsets.popper;
    var refOffsets = data.offsets.reference;

// using floor because the reference offsets may contain decimals we are not going to consider here
 var floor = Math.floor;
 var overlapsRef =
 (placement === 'left' &&
 floor(popperOffsets.right) > floor(refOffsets.left)) ||
 (placement === 'right' &&
 floor(popperOffsets.left) < floor(refOffsets.right)) ||
 (placement === 'top' &&
 floor(popperOffsets.bottom) > floor(refOffsets.top)) ||
 (placement === 'bottom' &&
 floor(popperOffsets.top) < floor(refOffsets.bottom));

var overflowsLeft = floor(popperOffsets.left) < floor(boundaries.left);
 var overflowsRight = floor(popperOffsets.right) > floor(boundaries.right);
 var overflowsTop = floor(popperOffsets.top) < floor(boundaries.top);
 var overflowsBottom =
 floor(popperOffsets.bottom) > floor(boundaries.bottom);

var overflowsBoundaries =
      (placement === 'left' && overflowsLeft) ||
      (placement === 'right' && overflowsRight) ||
      (placement === 'top' && overflowsTop) ||
      (placement === 'bottom' && overflowsBottom);

// flip the variation if required
    var isVertical = ['top', 'bottom'].indexOf(placement) !== -1;

// flips variation if reference element overflows boundaries
    var flippedVariationByRef =
      !!options.flipVariations &&
      ((isVertical && variation === 'start' && overflowsLeft) ||
        (isVertical && variation === 'end' && overflowsRight) ||
        (!isVertical && variation === 'start' && overflowsTop) ||
        (!isVertical && variation === 'end' && overflowsBottom));

// flips variation if popper content overflows boundaries
    var flippedVariationByContent =
      !!options.flipVariationsByContent &&
      ((isVertical && variation === 'start' && overflowsRight) ||
        (isVertical && variation === 'end' && overflowsLeft) ||
        (!isVertical && variation === 'start' && overflowsBottom) ||
        (!isVertical && variation === 'end' && overflowsTop));

var flippedVariation = flippedVariationByRef || flippedVariationByContent;

if (overlapsRef || overflowsBoundaries || flippedVariation) {
      // this boolean to detect any flip loop
      data.flipped = true;

if (overlapsRef || overflowsBoundaries) {
        placement = flipOrder[index + 1];
      }

if (flippedVariation) {
        variation = getOppositeVariation(variation);
      }

data.placement = placement + (variation ? '-' + variation : '');

// this object contains `position`, we want to preserve it along with
      // any additional property we may add in the future
      data.offsets.popper = Object.assign({}, data.offsets.popper,
        getPopperOffsets(
          data.instance.popper,
          data.offsets.reference,
          data.placement
        ));

data = runModifiers(data.instance.modifiers, data, 'flip');
    }
  });
  return data;
}

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by update method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function keepTogether(data) {
  var ref = data.offsets;
  var popper = ref.popper;
  var reference = ref.reference;
  var placement = data.placement.split('-')[0];
  var floor = Math.floor;
  var isVertical = ['top', 'bottom'].indexOf(placement) !== -1;
  var side = isVertical ? 'right' : 'bottom';
  var opSide = isVertical ? 'left' : 'top';
  var measurement = isVertical ? 'width' : 'height';

if (popper[side] < floor(reference[opSide])) {
 data.offsets.popper[opSide] =
 floor(reference[opSide]) - popper[measurement];
 }
 if (popper[opSide] > floor(reference[side])) {
 data.offsets.popper[opSide] = floor(reference[side]);
 }

return data;
}

/**
 * Converts a string containing value + unit into a px value number
 * @function
 * @memberof {modifiers~offset}
 * @private
 * @argument {String} str - Value + unit string
 * @argument {String} measurement - `height` or `width`
 * @argument {Object} popperOffsets
 * @argument {Object} referenceOffsets
 * @returns {Number|String}
 * Value in pixels, or original string if no values were extracted
 */
function toValue(str, measurement, popperOffsets, referenceOffsets) {
  // separate value from unit
  var split = str.match(/((?:\-|\+)?\d*\.?\d*)(.*)/);
  var value = +split[1];
  var unit = split[2];

// If it's not a number it's an operator, I guess
  if (!value) {
    return str;
  }

if (unit.indexOf('%') === 0) {
    var element;
    switch (unit) {
      case '%p':
        element = popperOffsets;
        break;
      case '%':
      case '%r':
      default:
        element = referenceOffsets;
    }

/**
 * Parse an `offset` string to extrapolate `x` and `y` numeric offsets.
 * @function
 * @memberof {modifiers~offset}
 * @private
 * @argument {String} offset
 * @argument {Object} popperOffsets
 * @argument {Object} referenceOffsets
 * @argument {String} basePlacement
 * @returns {Array} a two cells array with x and y offsets in numbers
 */
function parseOffset(
  offset,
  popperOffsets,
  referenceOffsets,
  basePlacement
) {
  var offsets = [0, 0];

// Use height if placement is left or right and index is 0 otherwise use width
  // in this way the first offset will use an axis and the second one
  // will use the other one
  var useHeight = ['right', 'left'].indexOf(basePlacement) !== -1;

// Split the offset string to obtain a list of values and operands
  // The regex addresses values with the plus or minus sign in front (+10, -20, etc)
  var fragments = offset.split(/(\+|\-)/).map(function (frag) { return frag.trim(); });

// Detect if the offset string contains a pair of values or a single one
  // they could be separated by comma or space
  var divider = fragments.indexOf(
    find(fragments, function (frag) { return frag.search(/,|\s/) !== -1; })
  );

if (fragments[divider] && fragments[divider].indexOf(',') === -1) {
    console.warn(
      'Offsets separated by white space(s) are deprecated, use a comma (,) instead.'
    );
  }

// If divider is found, we divide the list of values and operands to divide
  // them by ofset X and Y.
  var splitRegex = /\s*,\s*|\s+/;
  var ops = divider !== -1
    ? [
        fragments
          .slice(0, divider)
          .concat([fragments[divider].split(splitRegex)[0]]),
        [fragments[divider].split(splitRegex)[1]].concat(
          fragments.slice(divider + 1)
        ) ]
    : [fragments];

// Convert the values with units to absolute pixels to allow our computations
  ops = ops.map(function (op, index) {
    // Most of the units rely on the orientation of the popper
    var measurement = (index === 1 ? !useHeight : useHeight)
      ? 'height'
      : 'width';
    var mergeWithPrevious = false;
    return (
      op
        // This aggregates any `+` or `-` sign that aren't considered operators
        // e.g.: 10 + +5 => [10, +, +5]
        .reduce(function (a, b) {
          if (a[a.length - 1] === '' && ['+', '-'].indexOf(b) !== -1) {
            a[a.length - 1] = b;
            mergeWithPrevious = true;
            return a;
          } else if (mergeWithPrevious) {
            a[a.length - 1] += b;
            mergeWithPrevious = false;
            return a;
          } else {
            return a.concat(b);
          }
        }, [])
        // Here we convert the string values into number values (in px)
        .map(function (str) { return toValue(str, measurement, popperOffsets, referenceOffsets); })
    );
  });

// Loop trough the offsets arrays and execute the operations
  ops.forEach(function (op, index) {
    op.forEach(function (frag, index2) {
      if (isNumeric(frag)) {
        offsets[index] += frag * (op[index2 - 1] === '-' ? -1 : 1);
      }
    });
  });
  return offsets;
}

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by update method
 * @argument {Object} options - Modifiers configuration and options
 * @argument {Number|String} options.offset=0
 * The offset value as described in the modifier description
 * @returns {Object} The data object, properly modified
 */
function offset(data, ref) {
  var offset = ref.offset;

var placement = data.placement;
  var data_offsets = data.offsets;
  var popper = data_offsets.popper;
  var reference = data_offsets.reference;
  var basePlacement = placement.split('-')[0];

var offsets;
  if (isNumeric(+offset)) {
    offsets = [+offset, 0];
  } else {
    offsets = parseOffset(offset, popper, reference, basePlacement);
  }

if (basePlacement === 'left') {
    popper.top += offsets[0];
    popper.left -= offsets[1];
  } else if (basePlacement === 'right') {
    popper.top += offsets[0];
    popper.left += offsets[1];
  } else if (basePlacement === 'top') {
    popper.left += offsets[0];
    popper.top -= offsets[1];
  } else if (basePlacement === 'bottom') {
    popper.left += offsets[0];
    popper.top += offsets[1];
  }

data.popper = popper;
  return data;
}

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function preventOverflow(data, options) {
  var boundariesElement =
    options.boundariesElement || getOffsetParent(data.instance.popper);

// If offsetParent is the reference element, we really want to
  // go one step up and use the next offsetParent as reference to
  // avoid to make this modifier completely useless and look like broken
  if (data.instance.reference === boundariesElement) {
    boundariesElement = getOffsetParent(boundariesElement);
  }

// NOTE: DOM access here
  // resets the popper's position so that the document size can be calculated excluding
  // the size of the popper element itself
  var transformProp = getSupportedPropertyName('transform');
  var popperStyles = data.instance.popper.style; // assignment to help minification
  var top = popperStyles.top;
  var left = popperStyles.left;
  var transform = popperStyles[transformProp];
  popperStyles.top = '';
  popperStyles.left = '';
  popperStyles[transformProp] = '';

var boundaries = getBoundaries(
    data.instance.popper,
    data.instance.reference,
    options.padding,
    boundariesElement,
    data.positionFixed
  );

// NOTE: DOM access here
  // restores the original style properties after the offsets have been computed
  popperStyles.top = top;
  popperStyles.left = left;
  popperStyles[transformProp] = transform;

options.boundaries = boundaries;

var order = options.priority;
  var popper = data.offsets.popper;

var check = {
    primary: function primary(placement) {
      var obj;

var mainSide = placement === 'right' ? 'left' : 'top';
      var value = popper[mainSide];
      if (
        popper[placement] > boundaries[placement] &&
        !options.escapeWithReference
      ) {
        value = Math.min(
          popper[mainSide],
          boundaries[placement] -
            (placement === 'right' ? popper.width : popper.height)
        );
      }
      return ( obj = {}, obj[mainSide] = value, obj );
    },
  };

order.forEach(function (placement) {
    var side =
      ['left', 'top'].indexOf(placement) !== -1 ? 'primary' : 'secondary';
    popper = Object.assign({}, popper, check[side](placement));
  });

data.offsets.popper = popper;

return data;
}

var placement = data.placement;
  var basePlacement = placement.split('-')[0];
  var shiftvariation = placement.split('-')[1];

// if shift shiftvariation is specified, run the modifier
  if (shiftvariation) {
    var ref = data.offsets;
    var reference = ref.reference;
    var popper = ref.popper;
    var isVertical = ['bottom', 'top'].indexOf(basePlacement) !== -1;
    var side = isVertical ? 'left' : 'top';
    var measurement = isVertical ? 'width' : 'height';

var shiftOffsets = {
      start: ( obj = {}, obj[side] = reference[side], obj ),
      end: ( obj$1 = {}, obj$1[side] = reference[side] + reference[measurement] - popper[measurement], obj$1 ),
    };

data.offsets.popper = Object.assign({}, popper, shiftOffsets[shiftvariation]);
  }

return data;
}

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by update method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function hide(data) {
  if (!isModifierRequired(data.instance.modifiers, 'hide', 'preventOverflow')) {
    return data;
  }

var refRect = data.offsets.reference;
  var bound = find(
    data.instance.modifiers,
    function (modifier) { return modifier.name === 'preventOverflow'; }
  ).boundaries;

if (
 refRect.bottom < bound.top ||
 refRect.left > bound.right ||
 refRect.top > bound.bottom ||
 refRect.right < bound.left
 ) {
 // Avoid unnecessary DOM access if visibility hasn't changed
 if (data.hide === true) {
 return data;
 }

data.hide = true;
    data.attributes['x-out-of-boundaries'] = '';
  } else {
    // Avoid unnecessary DOM access if visibility hasn't changed
    if (data.hide === false) {
      return data;
    }

data.hide = false;
    data.attributes['x-out-of-boundaries'] = false;
  }

return data;
}

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
function inner(data) {
  var placement = data.placement;
  var basePlacement = placement.split('-')[0];
  var ref = data.offsets;
  var popper = ref.popper;
  var reference = ref.reference;
  var isHoriz = ['left', 'right'].indexOf(basePlacement) !== -1;

var subtractLength = ['top', 'left'].indexOf(basePlacement) === -1;

popper[isHoriz ? 'left' : 'top'] =
    reference[basePlacement] -
    (subtractLength ? popper[isHoriz ? 'width' : 'height'] : 0);

data.placement = getOppositePlacement(placement);
  data.offsets.popper = getClientRect(popper);

return data;
}

/**
 * Modifier function, each modifier can have a function of this type assigned
 * to its `fn` property. 
 * These functions will be called on each update, this means that you must
 * make sure they are performant enough to avoid performance bottlenecks.
 *
 * @function ModifierFn
 * @argument {dataObject} data - The data object generated by `update` method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {dataObject} The data object, properly modified
 */

/**
 * Modifiers are plugins used to alter the behavior of your poppers. 
 * Popper.js uses a set of 9 modifiers to provide all the basic functionalities
 * needed by the library.
 *
 * Usually you don't want to override the `order`, `fn` and `onLoad` props.
 * All the other properties are configurations that could be tweaked.
 * @namespace modifiers
 */
var modifiers = {
 /**
 * Modifier used to shift the popper on the start or end of its reference
 * element. 
 * It will read the variation of the `placement` property. 
 * It can be one either `-end` or `-start`.
 * @memberof modifiers
 * @inner
 */
 shift: {
 /** @prop {number} order=100 - Index used to define the order of execution */
 order: 100,
 /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
 enabled: true,
 /** @prop {ModifierFn} */
 fn: shift,
 },

/**
 * The `offset` modifier can shift your popper on both its axis.
 *
 * It accepts the following units:
 * - `px` or unit-less, interpreted as pixels
 * - `%` or `%r`, percentage relative to the length of the reference element
 * - `%p`, percentage relative to the length of the popper element
 * - `vw`, CSS viewport width unit
 * - `vh`, CSS viewport height unit
 *
 * For length is intended the main axis relative to the placement of the popper. 
 * This means that if the placement is `top` or `bottom`, the length will be the
 * `width`. In case of `left` or `right`, it will be the `height`.
 *
 * You can provide a single value (as `Number` or `String`), or a pair of values
 * as `String` divided by a comma or one (or more) white spaces. 
 * The latter is a deprecated method because it leads to confusion and will be
 * removed in v2. 
 * Additionally, it accepts additions and subtractions between different units.
 * Note that multiplications and divisions aren't supported.
 *
 * Valid examples are:
 * ```
 * 10
 * '10%'
 * '10, 10'
 * '10%, 10'
 * '10 + 10%'
 * '10 - 5vh + 3%'
 * '-10px + 5vh, 5px - 6%'
 * ```
 * > **NB**: If you desire to apply offsets to your poppers in a way that may make them overlap
 * > with their reference element, unfortunately, you will have to disable the `flip` modifier.
 * > You can read more on this at this [issue](https://github.com/FezVrasta/popper.js/issues/373).
 *
 * @memberof modifiers
 * @inner
 */
 offset: {
 /** @prop {number} order=200 - Index used to define the order of execution */
 order: 200,
 /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
 enabled: true,
 /** @prop {ModifierFn} */
 fn: offset,
 /** @prop {Number|String} offset=0
 * The offset value as described in the modifier description
 */
 offset: 0,
 },

/**
 * Modifier used to prevent the popper from being positioned outside the boundary.
 *
 * A scenario exists where the reference itself is not within the boundaries. 
 * We can say it has "escaped the boundaries" — or just "escaped". 
 * In this case we need to decide whether the popper should either:
 *
 * - detach from the reference and remain "trapped" in the boundaries, or
 * - if it should ignore the boundary and "escape with its reference"
 *
 * When `escapeWithReference` is set to`true` and reference is completely
 * outside its boundaries, the popper will overflow (or completely leave)
 * the boundaries in order to remain attached to the edge of the reference.
 *
 * @memberof modifiers
 * @inner
 */
 preventOverflow: {
 /** @prop {number} order=300 - Index used to define the order of execution */
 order: 300,
 /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
 enabled: true,
 /** @prop {ModifierFn} */
 fn: preventOverflow,
 /**
 * @prop {Array} [priority=['left','right','top','bottom']]
 * Popper will try to prevent overflow following these priorities by default,
 * then, it could overflow on the left and on top of the `boundariesElement`
 */
 priority: ['left', 'right', 'top', 'bottom'],
 /**
 * @prop {number} padding=5
 * Amount of pixel used to define a minimum distance between the boundaries
 * and the popper. This makes sure the popper always has a little padding
 * between the edges of its container
 */
 padding: 5,
 /**
 * @prop {String|HTMLElement} boundariesElement='scrollParent'
 * Boundaries used by the modifier. Can be `scrollParent`, `window`,
 * `viewport` or any DOM element.
 */
 boundariesElement: 'scrollParent',
 },

/**
   * Modifier used to make sure the reference and its popper stay near each other
   * without leaving any gap between the two. Especially useful when the arrow is
   * enabled and you want to ensure that it points to its reference element.
   * It cares only about the first axis. You can still have poppers with margin
   * between the popper and its reference element.
   * @memberof modifiers
   * @inner
   */
  keepTogether: {
    /** @prop {number} order=400 - Index used to define the order of execution */
    order: 400,
    /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
    enabled: true,
    /** @prop {ModifierFn} */
    fn: keepTogether,
  },

/**
   * This modifier is used to move the `arrowElement` of the popper to make
   * sure it is positioned between the reference element and its popper element.
   * It will read the outer size of the `arrowElement` node to detect how many
   * pixels of conjunction are needed.
   *
   * It has no effect if no `arrowElement` is provided.
   * @memberof modifiers
   * @inner
   */
  arrow: {
    /** @prop {number} order=500 - Index used to define the order of execution */
    order: 500,
    /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
    enabled: true,
    /** @prop {ModifierFn} */
    fn: arrow,
    /** @prop {String|HTMLElement} element='[x-arrow]' - Selector or node used as arrow */
    element: '[x-arrow]',
  },

/**
   * Modifier used to flip the popper's placement when it starts to overlap its
   * reference element.
   *
   * Requires the `preventOverflow` modifier before it in order to work.
   *
   * **NOTE:** this modifier will interrupt the current update cycle and will
   * restart it if it detects the need to flip the placement.
   * @memberof modifiers
   * @inner
   */
  flip: {
    /** @prop {number} order=600 - Index used to define the order of execution */
    order: 600,
    /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
    enabled: true,
    /** @prop {ModifierFn} */
    fn: flip,
    /**
     * @prop {String|Array} behavior='flip'
     * The behavior used to change the popper's placement. It can be one of
     * `flip`, `clockwise`, `counterclockwise` or an array with a list of valid
     * placements (with optional variations)
     */
    behavior: 'flip',
    /**
     * @prop {number} padding=5
     * The popper will flip if it hits the edges of the `boundariesElement`
     */
    padding: 5,
    /**
     * @prop {String|HTMLElement} boundariesElement='viewport'
     * The element which will define the boundaries of the popper position.
     * The popper will never be placed outside of the defined boundaries
     * (except if `keepTogether` is enabled)
     */
    boundariesElement: 'viewport',
    /**
     * @prop {Boolean} flipVariations=false
     * The popper will switch placement variation between `-start` and `-end` when
     * the reference element overlaps its boundaries.
     *
     * The original placement should have a set variation.
     */
    flipVariations: false,
    /**
     * @prop {Boolean} flipVariationsByContent=false
     * The popper will switch placement variation between `-start` and `-end` when
     * the popper element overlaps its reference boundaries.
     *
     * The original placement should have a set variation.
     */
    flipVariationsByContent: false,
  },

/**
   * Modifier used to make the popper flow toward the inner of the reference element.
   * By default, when this modifier is disabled, the popper will be placed outside
   * the reference element.
   * @memberof modifiers
   * @inner
   */
  inner: {
    /** @prop {number} order=700 - Index used to define the order of execution */
    order: 700,
    /** @prop {Boolean} enabled=false - Whether the modifier is enabled or not */
    enabled: false,
    /** @prop {ModifierFn} */
    fn: inner,
  },

/**
   * Modifier used to hide the popper when its reference element is outside of the
   * popper boundaries. It will set a `x-out-of-boundaries` attribute which can
   * be used to hide with a CSS selector the popper when its reference is
   * out of boundaries.
   *
   * Requires the `preventOverflow` modifier before it in order to work.
   * @memberof modifiers
   * @inner
   */
  hide: {
    /** @prop {number} order=800 - Index used to define the order of execution */
    order: 800,
    /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
    enabled: true,
    /** @prop {ModifierFn} */
    fn: hide,
  },

/**
   * Computes the style that will be applied to the popper element to gets
   * properly positioned.
   *
   * Note that this modifier will not touch the DOM, it just prepares the styles
   * so that `applyStyle` modifier can apply it. This separation is useful
   * in case you need to replace `applyStyle` with a custom implementation.
   *
   * This modifier has `850` as `order` value to maintain backward compatibility
   * with previous versions of Popper.js. Expect the modifiers ordering method
   * to change in future major versions of the library.
   *
   * @memberof modifiers
   * @inner
   */
  computeStyle: {
    /** @prop {number} order=850 - Index used to define the order of execution */
    order: 850,
    /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
    enabled: true,
    /** @prop {ModifierFn} */
    fn: computeStyle,
    /**
     * @prop {Boolean} gpuAcceleration=true
     * If true, it uses the CSS 3D transformation to position the popper.
     * Otherwise, it will use the `top` and `left` properties
     */
    gpuAcceleration: true,
    /**
     * @prop {string} [x='bottom']
     * Where to anchor the X axis (`bottom` or `top`). AKA X offset origin.
     * Change this if your popper should grow in a direction different from `bottom`
     */
    x: 'bottom',
    /**
     * @prop {string} [x='left']
     * Where to anchor the Y axis (`left` or `right`). AKA Y offset origin.
     * Change this if your popper should grow in a direction different from `right`
     */
    y: 'right',
  },

/**
   * Applies the computed styles to the popper element.
   *
   * All the DOM manipulations are limited to this modifier. This is useful in case
   * you want to integrate Popper.js inside a framework or view library and you
   * want to delegate all the DOM manipulations to it.
   *
   * Note that if you disable this modifier, you must make sure the popper element
   * has its position set to `absolute` before Popper.js can do its work!
   *
   * Just disable this modifier and define your own to achieve the desired effect.
   *
   * @memberof modifiers
   * @inner
   */
  applyStyle: {
    /** @prop {number} order=900 - Index used to define the order of execution */
    order: 900,
    /** @prop {Boolean} enabled=true - Whether the modifier is enabled or not */
    enabled: true,
    /** @prop {ModifierFn} */
    fn: applyStyle,
    /** @prop {Function} */
    onLoad: applyStyleOnLoad,
    /**
     * @deprecated since version 1.10.0, the property moved to `computeStyle` modifier
     * @prop {Boolean} gpuAcceleration=true
     * If true, it uses the CSS 3D transformation to position the popper.
     * Otherwise, it will use the `top` and `left` properties
     */
    gpuAcceleration: undefined,
  },
};

/**
 * The `dataObject` is an object containing all the information used by Popper.js.
 * This object is passed to modifiers and to the `onCreate` and `onUpdate` callbacks.
 * @name dataObject
 * @property {Object} data.instance The Popper.js instance
 * @property {String} data.placement Placement applied to popper
 * @property {String} data.originalPlacement Placement originally defined on init
 * @property {Boolean} data.flipped True if popper has been flipped by flip modifier
 * @property {Boolean} data.hide True if the reference element is out of boundaries, useful to know when to hide the popper
 * @property {HTMLElement} data.arrowElement Node used as arrow by arrow modifier
 * @property {Object} data.styles Any CSS property defined here will be applied to the popper. It expects the JavaScript nomenclature (eg. `marginBottom`)
 * @property {Object} data.arrowStyles Any CSS property defined here will be applied to the popper arrow. It expects the JavaScript nomenclature (eg. `marginBottom`)
 * @property {Object} data.boundaries Offsets of the popper boundaries
 * @property {Object} data.offsets The measurements of popper, reference and arrow elements
 * @property {Object} data.offsets.popper `top`, `left`, `width`, `height` values
 * @property {Object} data.offsets.reference `top`, `left`, `width`, `height` values
 * @property {Object} data.offsets.arrow] `top` and `left` offsets, only one of them will be different from 0
 */

/**
 * Default options provided to Popper.js constructor. 
 * These can be overridden using the `options` argument of Popper.js. 
 * To override an option, simply pass an object with the same
 * structure of the `options` object, as the 3rd argument. For example:
 * ```
 * new Popper(ref, pop, {
 * modifiers: {
 * preventOverflow: { enabled: false }
 * }
 * })
 * ```
 * @type {Object}
 * @static
 * @memberof Popper
 */
var Defaults = {
 /**
 * Popper's placement.
 * @prop {Popper.placements} placement='bottom'
 */
 placement: 'bottom',

/**
   * Set this to true if you want popper to position it self in 'fixed' mode
   * @prop {Boolean} positionFixed=false
   */
  positionFixed: false,

/**
   * Whether events (resize, scroll) are initially enabled.
   * @prop {Boolean} eventsEnabled=true
   */
  eventsEnabled: true,

/**
   * Set to true if you want to automatically remove the popper when
   * you call the `destroy` method.
   * @prop {Boolean} removeOnDestroy=false
   */
  removeOnDestroy: false,

/**
 * Callback called when the popper is created. 
 * By default, it is set to no-op. 
 * Access Popper.js instance with `data.instance`.
 * @prop {onCreate}
 */
 onCreate: function () {},

/**
 * Callback called when the popper is updated. This callback is not called
 * on the initialization/creation of the popper, but only on subsequent
 * updates. 
 * By default, it is set to no-op. 
 * Access Popper.js instance with `data.instance`.
 * @prop {onUpdate}
 */
 onUpdate: function () {},

/**
   * List of modifiers used to modify the offsets before they are applied to the popper.
   * They provide most of the functionalities of Popper.js.
   * @prop {modifiers}
   */
  modifiers: modifiers,
};

/**
 * @callback onCreate
 * @param {dataObject} data
 */

/**
 * @callback onUpdate
 * @param {dataObject} data
 */

// Utils

var Popper = function Popper(reference, popper, options) {
  var this$1 = this;
  if ( options === void 0 ) options = {};

// make update() debounced, so that it only runs at most once-per-tick
  this.update = debounce(this.update.bind(this));

this.scheduleUpdate = this.scheduleUpdate.bind(this);

// with {} we create a new object with the options inside it
  this.options = Object.assign({}, Popper.Defaults, options);

// init state
  this.state = {
    isDestroyed: false,
    isCreated: false,
    scrollParents: [],
  };

// get reference and popper elements (allow jQuery wrappers)
  this.reference = reference && reference.jquery ? reference[0] : reference;
  this.popper = popper && popper.jquery ? popper[0] : popper;

// Deep merge modifiers options
  this.options.modifiers = {};
  Object.keys(Object.assign({}, Popper.Defaults.modifiers,
    options.modifiers)).forEach(function (name) {
    this$1.options.modifiers[name] = Object.assign({}, (Popper.Defaults.modifiers[name] || {}),
      // If there are custom options, override and merge with default ones
      (options.modifiers ? options.modifiers[name] : {}));
  });

// Refactoring modifiers' list (Object => Array)
  this.modifiers = Object.keys(this.options.modifiers)
    .map(function (name) { return (Object.assign({}, {name: name},
      this$1.options.modifiers[name])); })
    // sort the modifiers by order
    .sort(function (a, b) { return a.order - b.order; });

// modifiers have the ability to execute arbitrary code when Popper.js get inited
  // such code is executed in the same order of its modifier
  // they could add new properties to their options configuration
  // BE AWARE: don't add options to `options.modifiers.name` but to `modifierOptions`!
  this.modifiers.forEach(function (modifierOptions) {
    if (modifierOptions.enabled && isFunction(modifierOptions.onLoad)) {
      modifierOptions.onLoad(
        this$1.reference,
        this$1.popper,
        this$1.options,
        modifierOptions,
        this$1.state
      );
    }
  });

// fire the first update to position the popper in the right place
  this.update();

var eventsEnabled = this.options.eventsEnabled;
  if (eventsEnabled) {
    // setup event listeners, they will take care of update the position in specific situations
    this.enableEventListeners();
  }

this.state.eventsEnabled = eventsEnabled;
};

// We can't use class properties because they don't get listed in the
// class prototype and break stuff like Sinon stubs
Popper.prototype.update = function update$1 () {
 return update.call(this);
};
Popper.prototype.destroy = function destroy$1 () {
 return destroy.call(this);
};
Popper.prototype.enableEventListeners = function enableEventListeners$1 () {
 return enableEventListeners.call(this);
};
Popper.prototype.disableEventListeners = function disableEventListeners$1 () {
 return disableEventListeners.call(this);
};
/**
 * Schedules an update. It will run on the next UI update available.
 * @method scheduleUpdate
 * @memberof Popper
 */
Popper.prototype.scheduleUpdate = function scheduleUpdate () {
 return requestAnimationFrame(this.update);
};
/**
 * Collection of utilities useful when writing custom modifiers.
 * Starting from version 1.7, this method is available only if you
 * include `popper-utils.js` before `popper.js`.
 *
 * **DEPRECATION**: This way to access PopperUtils is deprecated
 * and will be removed in v2! Use the PopperUtils module directly instead.
 * Due to the high instability of the methods contained in Utils, we can't
 * guarantee them to follow semver. Use them at your own risk!
 * @static
 * @private
 * @type {Object}
 * @deprecated since version 1.8
 * @member Utils
 * @memberof Popper
 */
Popper.Utils = (typeof window !== 'undefined' ? window : global).PopperUtils;
Popper.placements = placements;
Popper.Defaults = Defaults;
/**
 * The `referenceObject` is an object that provides an interface compatible with Popper.js
 * and lets you use it as replacement of a real DOM node. 
 * You can use this method to position a popper relatively to a set of coordinates
 * in case you don't have a DOM node to use as reference.
 *
 * ```
 * new Popper(referenceObject, popperNode);
 * ```
 *
 * NB: This feature isn't supported in Internet Explorer 10.
 * @name referenceObject
 * @property {Function} data.getBoundingClientRect
 * A function that returns a set of coordinates compatible with the native `getBoundingClientRect` method.
 * @property {number} data.clientWidth
 * An ES6 getter that will return the width of the virtual reference element.
 * @property {number} data.clientHeight
 * An ES6 getter that will return the height of the virtual reference element.
 */

export default Popper;

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