understrap/js/popper.js

/**!
 * @fileOverview Kickass library to create and place poppers near their reference elements.
 * @version 1.11.0
 * @license
 * Copyright (c) 2016 Federico Zivolo and contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
const nativeHints = ['native code', '[object MutationObserverConstructor]'];

/**
 * Determine if a function is implemented natively (as opposed to a polyfill).
 * @method
 * @memberof Popper.Utils
 * @argument {Function | undefined} fn the function to check
 * @returns {Boolean}
 */
var isNative = (fn => nativeHints.some(hint => (fn || '').toString().indexOf(hint) > -1));

const isBrowser = typeof window !== 'undefined';
const longerTimeoutBrowsers = ['Edge', 'Trident', 'Firefox'];
let timeoutDuration = 0;
for (let i = 0; i < longerTimeoutBrowsers.length; i += 1) {
  if (isBrowser && navigator.userAgent.indexOf(longerTimeoutBrowsers[i]) >= 0) {
    timeoutDuration = 1;
    break;
  }
}

function microtaskDebounce(fn) {
  let scheduled = false;
  let i = 0;
  const elem = document.createElement('span');

  // MutationObserver provides a mechanism for scheduling microtasks, which
  // are scheduled *before* the next task. This gives us a way to debounce
  // a function but ensure it's called *before* the next paint.
  const observer = new MutationObserver(() => {
    fn();
    scheduled = false;
  });

  observer.observe(elem, { attributes: true });

  return () => {
    if (!scheduled) {
      scheduled = true;
      elem.setAttribute('x-index', i);
      i = i + 1; // don't use compund (+=) because it doesn't get optimized in V8
    }
  };
}

function taskDebounce(fn) {
  let scheduled = false;
  return () => {
    if (!scheduled) {
      scheduled = true;
      setTimeout(() => {
        scheduled = false;
        fn();
      }, timeoutDuration);
    }
  };
}

// It's common for MutationObserver polyfills to be seen in the wild, however
// these rely on Mutation Events which only occur when an element is connected
// to the DOM. The algorithm used in this module does not use a connected element,
// and so we must ensure that a *native* MutationObserver is available.
const supportsNativeMutationObserver = isBrowser && isNative(window.MutationObserver);

/**
* 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 = supportsNativeMutationObserver ? 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) {
  const 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
  const 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 || ['HTML', 'BODY', '#document'].indexOf(element.nodeName) !== -1) {
    return window.document.body;
  }

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

  return getScrollParent(getParentNode(element));
}

/**
 * Returns the offset parent of the given element
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} offset parent
 */
function getOffsetParent(element) {
  // NOTE: 1 DOM access here
  const offsetParent = element && element.offsetParent;
  const nodeName = offsetParent && offsetParent.nodeName;

  if (!nodeName || nodeName === 'BODY' || nodeName === 'HTML') {
    return window.document.documentElement;
  }

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

  return offsetParent;
}

function isOffsetContainer(element) {
  const { nodeName } = element;
  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 window.document.documentElement;
  }

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

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

  // 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
  const 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 = 'top') {
  const upperSide = side === 'top' ? 'scrollTop' : 'scrollLeft';
  const nodeName = element.nodeName;

  if (nodeName === 'BODY' || nodeName === 'HTML') {
    const html = window.document.documentElement;
    const scrollingElement = window.document.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 = false) {
  const scrollTop = getScroll(element, 'top');
  const scrollLeft = getScroll(element, 'left');
  const 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) {
  const sideA = axis === 'x' ? 'Left' : 'Top';
  const sideB = sideA === 'Left' ? 'Right' : 'Bottom';

  return +styles[`border${sideA}Width`].split('px')[0] + +styles[`border${sideB}Width`].split('px')[0];
}

/**
 * Tells if you are running Internet Explorer 10
 * @method
 * @memberof Popper.Utils
 * @returns {Boolean} isIE10
 */
let isIE10 = undefined;

var isIE10$1 = function () {
  if (isIE10 === undefined) {
    isIE10 = navigator.appVersion.indexOf('MSIE 10') !== -1;
  }
  return isIE10;
};

function getSize(axis, body, html, computedStyle) {
  return Math.max(body[`offset${axis}`], html[`client${axis}`], html[`offset${axis}`], isIE10$1() ? html[`offset${axis}`] + computedStyle[`margin${axis === 'Height' ? 'Top' : 'Left'}`] + computedStyle[`margin${axis === 'Height' ? 'Bottom' : 'Right'}`] : 0);
}

function getWindowSizes() {
  const body = window.document.body;
  const html = window.document.documentElement;
  const computedStyle = isIE10$1() && window.getComputedStyle(html);

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

var _extends = Object.assign || function (target) {
  for (var i = 1; i < arguments.length; i++) {
    var source = arguments[i];

    for (var key in source) {
      if (Object.prototype.hasOwnProperty.call(source, key)) {
        target[key] = source[key];
      }
    }
  }

  return target;
};

/**
 * 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 _extends({}, 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) {
  let 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
  if (isIE10$1()) {
    try {
      rect = element.getBoundingClientRect();
      const scrollTop = getScroll(element, 'top');
      const scrollLeft = getScroll(element, 'left');
      rect.top += scrollTop;
      rect.left += scrollLeft;
      rect.bottom += scrollTop;
      rect.right += scrollLeft;
    } catch (err) {}
  } else {
    rect = element.getBoundingClientRect();
  }

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

  // subtract scrollbar size from sizes
  const sizes = element.nodeName === 'HTML' ? getWindowSizes() : {};
  const width = sizes.width || element.clientWidth || result.right - result.left;
  const height = sizes.height || element.clientHeight || result.bottom - result.top;

  let horizScrollbar = element.offsetWidth - width;
  let 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) {
    const styles = getStyleComputedProperty(element);
    horizScrollbar -= getBordersSize(styles, 'x');
    vertScrollbar -= getBordersSize(styles, 'y');

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

  return getClientRect(result);
}

function getOffsetRectRelativeToArbitraryNode(children, parent) {
  const isIE10 = isIE10$1();
  const isHTML = parent.nodeName === 'HTML';
  const childrenRect = getBoundingClientRect(children);
  const parentRect = getBoundingClientRect(parent);
  const scrollParent = getScrollParent(children);

  const styles = getStyleComputedProperty(parent);
  const borderTopWidth = +styles.borderTopWidth.split('px')[0];
  const borderLeftWidth = +styles.borderLeftWidth.split('px')[0];

  let 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) {
    const marginTop = +styles.marginTop.split('px')[0];
    const marginLeft = +styles.marginLeft.split('px')[0];

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

  return offsets;
}

function getViewportOffsetRectRelativeToArtbitraryNode(element) {
  const html = window.document.documentElement;
  const relativeOffset = getOffsetRectRelativeToArbitraryNode(element, html);
  const width = Math.max(html.clientWidth, window.innerWidth || 0);
  const height = Math.max(html.clientHeight, window.innerHeight || 0);

  const scrollTop = getScroll(html);
  const scrollLeft = getScroll(html, 'left');

  const offset = {
    top: scrollTop - relativeOffset.top + relativeOffset.marginTop,
    left: scrollLeft - relativeOffset.left + relativeOffset.marginLeft,
    width,
    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) {
  const nodeName = element.nodeName;
  if (nodeName === 'BODY' || nodeName === 'HTML') {
    return false;
  }
  if (getStyleComputedProperty(element, 'position') === 'fixed') {
    return true;
  }
  return isFixed(getParentNode(element));
}

/**
 * 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
 * @returns {Object} Coordinates of the boundaries
 */
function getBoundaries(popper, reference, padding, boundariesElement) {
  // NOTE: 1 DOM access here
  let boundaries = { top: 0, left: 0 };
  const offsetParent = findCommonOffsetParent(popper, reference);

  // Handle viewport case
  if (boundariesElement === 'viewport') {
    boundaries = getViewportOffsetRectRelativeToArtbitraryNode(offsetParent);
  } else {
    // Handle other cases based on DOM element used as boundaries
    let boundariesNode;
    if (boundariesElement === 'scrollParent') {
      boundariesNode = getScrollParent(getParentNode(popper));
      if (boundariesNode.nodeName === 'BODY') {
        boundariesNode = window.document.documentElement;
      }
    } else if (boundariesElement === 'window') {
      boundariesNode = window.document.documentElement;
    } else {
      boundariesNode = boundariesElement;
    }

    const offsets = getOffsetRectRelativeToArbitraryNode(boundariesNode, offsetParent);

    // In case of HTML, we need a different computation
    if (boundariesNode.nodeName === 'HTML' && !isFixed(offsetParent)) {
      const { height, width } = getWindowSizes();
      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
  boundaries.left += padding;
  boundaries.top += padding;
  boundaries.right -= padding;
  boundaries.bottom -= padding;

  return boundaries;
}

function getArea({ width, 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 = 0) {
  if (placement.indexOf('auto') === -1) {
    return placement;
  }

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

  const 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
    }
  };

  const sortedAreas = Object.keys(rects).map(key => _extends({
    key
  }, rects[key], {
    area: getArea(rects[key])
  })).sort((a, b) => b.area - a.area);

  const filteredAreas = sortedAreas.filter(({ width, height }) => width >= popper.clientWidth && height >= popper.clientHeight);

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

  const 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)
 * @returns {Object} An object containing the offsets which will be applied to the popper
 */
function getReferenceOffsets(state, popper, reference) {
  const commonOffsetParent = findCommonOffsetParent(popper, reference);
  return getOffsetRectRelativeToArbitraryNode(reference, commonOffsetParent);
}

/**
 * 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) {
  const styles = window.getComputedStyle(element);
  const x = parseFloat(styles.marginTop) + parseFloat(styles.marginBottom);
  const y = parseFloat(styles.marginLeft) + parseFloat(styles.marginRight);
  const 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) {
  const hash = { left: 'right', right: 'left', bottom: 'top', top: 'bottom' };
  return placement.replace(/left|right|bottom|top/g, matched => 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
  const popperRect = getOuterSizes(popper);

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

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

  // use `find` + `indexOf` if `findIndex` isn't supported
  const match = find(arr, obj => 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) {
  const modifiersToRun = ends === undefined ? modifiers : modifiers.slice(0, findIndex(modifiers, 'name', ends));

  modifiersToRun.forEach(modifier => {
    if (modifier.function) {
      console.warn('`modifier.function` is deprecated, use `modifier.fn`!');
    }
    const fn = modifier.function || modifier.fn;
    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.<br />
 * 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;
  }

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

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

  // 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;

  // compute the popper offsets
  data.offsets.popper = getPopperOffsets(this.popper, data.offsets.reference, data.placement);
  data.offsets.popper.position = '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(({ name, enabled }) => 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) {
  const prefixes = [false, 'ms', 'Webkit', 'Moz', 'O'];
  const upperProp = property.charAt(0).toUpperCase() + property.slice(1);

  for (let i = 0; i < prefixes.length - 1; i++) {
    const prefix = prefixes[i];
    const toCheck = prefix ? `${prefix}${upperProp}` : property;
    if (typeof window.document.body.style[toCheck] !== 'undefined') {
      return toCheck;
    }
  }
  return null;
}

/**
 * Destroy 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.left = '';
    this.popper.style.position = '';
    this.popper.style.top = '';
    this.popper.style[getSupportedPropertyName('transform')] = '';
  }

  this.disableEventListeners();

  // remove the popper if user explicity 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;
}

function attachToScrollParents(scrollParent, event, callback, scrollParents) {
  const isBody = scrollParent.nodeName === 'BODY';
  const target = isBody ? window : 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;
  window.addEventListener('resize', state.updateBound, { passive: true });

  // Scroll event listener on scroll parents
  const 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
  window.removeEventListener('resize', state.updateBound);

  // Remove scroll event listener on scroll parents
  state.scrollParents.forEach(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) {
    window.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(prop => {
    let 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) {
    const 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 the arrow style has been computed, apply the arrow style
  if (data.offsets.arrow) {
    setStyles(data.arrowElement, data.offsets.arrow);
  }

  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
  const referenceOffsets = getReferenceOffsets(state, popper, reference);

  // 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
  const 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: 'absolute' });

  return options;
}

/**
 * @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) {
  const { x, y } = options;
  const { popper } = data.offsets;

  // Remove this legacy support in Popper.js v2
  const legacyGpuAccelerationOption = find(data.instance.modifiers, modifier => 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!');
  }
  const gpuAcceleration = legacyGpuAccelerationOption !== undefined ? legacyGpuAccelerationOption : options.gpuAcceleration;

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

  // Styles
  const styles = {
    position: popper.position
  };

  // floor sides to avoid blurry text
  const offsets = {
    left: Math.floor(popper.left),
    top: Math.floor(popper.top),
    bottom: Math.floor(popper.bottom),
    right: Math.floor(popper.right)
  };

  const sideA = x === 'bottom' ? 'top' : 'bottom';
  const 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
  const 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.
  let left, top;
  if (sideA === 'bottom') {
    top = -offsetParentRect.height + offsets.bottom;
  } else {
    top = offsets.top;
  }
  if (sideB === 'right') {
    left = -offsetParentRect.width + offsets.right;
  } else {
    left = offsets.left;
  }
  if (gpuAcceleration && prefixedProperty) {
    styles[prefixedProperty] = `translate3d(${left}px, ${top}px, 0)`;
    styles[sideA] = 0;
    styles[sideB] = 0;
    styles.willChange = 'transform';
  } else {
    // othwerise, we use the standard `top`, `left`, `bottom` and `right` properties
    const invertTop = sideA === 'bottom' ? -1 : 1;
    const invertLeft = sideB === 'right' ? -1 : 1;
    styles[sideA] = top * invertTop;
    styles[sideB] = left * invertLeft;
    styles.willChange = `${sideA}, ${sideB}`;
  }

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

  // Update attributes and styles of `data`
  data.attributes = _extends({}, attributes, data.attributes);
  data.styles = _extends({}, styles, data.styles);

  return data;
}

/**
 * Helper used to know if the given modifier depends from another one.<br />
 * 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) {
  const requesting = find(modifiers, ({ name }) => name === requestingName);

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

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

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

  let 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;
    }
  }

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

  const len = isVertical ? 'height' : 'width';
  const side = isVertical ? 'top' : 'left';
  const altSide = isVertical ? 'left' : 'top';
  const opSide = isVertical ? 'bottom' : 'right';
  const arrowElementSize = getOuterSizes(arrowElement)[len];

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

  // 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];
  }

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

  // Compute the sideValue using the updated popper offsets
  let sideValue = center - getClientRect(data.offsets.popper)[side];

  // 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 = {};
  data.offsets.arrow[side] = Math.round(sideValue);
  data.offsets.arrow[altSide] = ''; // make sure to unset any eventual altSide value from the DOM node

  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.<br />
 * 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.<br />
 * 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-right` (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`
const 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 = false) {
  const index = validPlacements.indexOf(placement);
  const arr = validPlacements.slice(index + 1).concat(validPlacements.slice(0, index));
  return counter ? arr.reverse() : arr;
}

const 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;
  }

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

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

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

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

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

    // using floor because the reference offsets may contain decimals we are not going to consider here
    const floor = Math.floor;
    const 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);

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

    const overflowsBoundaries = placement === 'left' && overflowsLeft || placement === 'right' && overflowsRight || placement === 'top' && overflowsTop || placement === 'bottom' && overflowsBottom;

    // flip the variation if required
    const isVertical = ['top', 'bottom'].indexOf(placement) !== -1;
    const flippedVariation = !!options.flipVariations && (isVertical && variation === 'start' && overflowsLeft || isVertical && variation === 'end' && overflowsRight || !isVertical && variation === 'start' && overflowsTop || !isVertical && variation === 'end' && overflowsBottom);

    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 = _extends({}, 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) {
  const { popper, reference } = data.offsets;
  const placement = data.placement.split('-')[0];
  const floor = Math.floor;
  const isVertical = ['top', 'bottom'].indexOf(placement) !== -1;
  const side = isVertical ? 'right' : 'bottom';
  const opSide = isVertical ? 'left' : 'top';
  const 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
  const split = str.match(/((?:\-|\+)?\d*\.?\d*)(.*)/);
  const value = +split[1];
  const unit = split[2];

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

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

    const rect = getClientRect(element);
    return rect[measurement] / 100 * value;
  } else if (unit === 'vh' || unit === 'vw') {
    // if is a vh or vw, we calculate the size based on the viewport
    let size;
    if (unit === 'vh') {
      size = Math.max(document.documentElement.clientHeight, window.innerHeight || 0);
    } else {
      size = Math.max(document.documentElement.clientWidth, window.innerWidth || 0);
    }
    return size / 100 * value;
  } else {
    // if is an explicit pixel unit, we get rid of the unit and keep the value
    // if is an implicit unit, it's px, and we return just the value
    return value;
  }
}

/**
 * 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) {
  const 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
  const 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)
  const fragments = offset.split(/(\+|\-)/).map(frag => frag.trim());

  // Detect if the offset string contains a pair of values or a single one
  // they could be separated by comma or space
  const divider = fragments.indexOf(find(fragments, frag => 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.
  const splitRegex = /\s*,\s*|\s+/;
  let 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((op, index) => {
    // Most of the units rely on the orientation of the popper
    const measurement = (index === 1 ? !useHeight : useHeight) ? 'height' : 'width';
    let mergeWithPrevious = false;
    return op
    // This aggregates any `+` or `-` sign that aren't considered operators
    // e.g.: 10 + +5 => [10, +, +5]
    .reduce((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(str => toValue(str, measurement, popperOffsets, referenceOffsets));
  });

  // Loop trough the offsets arrays and execute the operations
  ops.forEach((op, index) => {
    op.forEach((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, { offset }) {
  const { placement, offsets: { popper, reference } } = data;
  const basePlacement = placement.split('-')[0];

  let 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) {
  let 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);
  }

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

  const order = options.priority;
  let popper = data.offsets.popper;

  const check = {
    primary(placement) {
      let value = popper[placement];
      if (popper[placement] < boundaries[placement] && !options.escapeWithReference) {
        value = Math.max(popper[placement], boundaries[placement]);
      }
      return { [placement]: value };
    },
    secondary(placement) {
      const mainSide = placement === 'right' ? 'left' : 'top';
      let value = popper[mainSide];
      if (popper[placement] > boundaries[placement] && !options.escapeWithReference) {
        value = Math.min(popper[mainSide], boundaries[placement] - (placement === 'right' ? popper.width : popper.height));
      }
      return { [mainSide]: value };
    }
  };

  order.forEach(placement => {
    const side = ['left', 'top'].indexOf(placement) !== -1 ? 'primary' : 'secondary';
    popper = _extends({}, popper, check[side](placement));
  });

  data.offsets.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 shift(data) {
  const placement = data.placement;
  const basePlacement = placement.split('-')[0];
  const shiftvariation = placement.split('-')[1];

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

    const shiftOffsets = {
      start: { [side]: reference[side] },
      end: {
        [side]: reference[side] + reference[measurement] - popper[measurement]
      }
    };

    data.offsets.popper = _extends({}, 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;
  }

  const refRect = data.offsets.reference;
  const bound = find(data.instance.modifiers, modifier => 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) {
  const placement = data.placement;
  const basePlacement = placement.split('-')[0];
  const { popper, reference } = data.offsets;
  const isHoriz = ['left', 'right'].indexOf(basePlacement) !== -1;

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

  popper[isHoriz ? 'left' : 'top'] = reference[placement] - (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.<br />
 * 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.<br />
 * 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.<br />
   * It will read the variation of the `placement` property.<br />
   * 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 unitless, 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.<br />
   * 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.<br />
   * The latter is a deprecated method because it leads to confusion and will be
   * removed in v2.<br />
   * 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%'
   * ```
   *
   * @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.
   *
   * An scenario exists where the reference itself is not within the boundaries.<br />
   * We can say it has "escaped the boundaries" — or just "escaped".<br />
   * 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 has always 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 eachothers
   * without leaving any gap between the two. Expecially useful when the arrow is
   * enabled and you want to assure it to point 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 conjuction 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'
  },

  /**
   * 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 you 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 informations used by Popper.js
 * this object get 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.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.<br />
 * These can be overriden using the `options` argument of Popper.js.<br />
 * To override an option, simply pass as 3rd argument an object with the same
 * structure of this object, 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',

  /**
   * 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.<br />
   * By default, is set to no-op.<br />
   * Access Popper.js instance with `data.instance`.
   * @prop {onCreate}
   */
  onCreate: () => {},

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

  /**
   * 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
};

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

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

// Utils
// Methods
class Popper {
  /**
   * Create a new Popper.js instance
   * @class Popper
   * @param {HTMLElement|referenceObject} reference - The reference element used to position the popper
   * @param {HTMLElement} popper - The HTML element used as popper.
   * @param {Object} options - Your custom options to override the ones defined in [Defaults](#defaults)
   * @return {Object} instance - The generated Popper.js instance
   */
  constructor(reference, popper, options = {}) {
    this.scheduleUpdate = () => requestAnimationFrame(this.update);

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

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

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

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

    // Deep merge modifiers options
    this.options.modifiers = {};
    Object.keys(_extends({}, Popper.Defaults.modifiers, options.modifiers)).forEach(name => {
      this.options.modifiers[name] = _extends({}, Popper.Defaults.modifiers[name] || {}, options.modifiers ? options.modifiers[name] : {});
    });

    // Refactoring modifiers' list (Object => Array)
    this.modifiers = Object.keys(this.options.modifiers).map(name => _extends({
      name
    }, this.options.modifiers[name]))
    // sort the modifiers by order
    .sort((a, b) => 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(modifierOptions => {
      if (modifierOptions.enabled && isFunction(modifierOptions.onLoad)) {
        modifierOptions.onLoad(this.reference, this.popper, this.options, modifierOptions, this.state);
      }
    });

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

    const 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
  update() {
    return update.call(this);
  }
  destroy() {
    return destroy.call(this);
  }
  enableEventListeners() {
    return enableEventListeners.call(this);
  }
  disableEventListeners() {
    return disableEventListeners.call(this);
  }

  /**
   * Schedule an update, it will run on the next UI update available
   * @method scheduleUpdate
   * @memberof Popper
   */


  /**
   * 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
   */
}

/**
 * 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.<br />
 * 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.
 */

Popper.Utils = (typeof window !== 'undefined' ? window : global).PopperUtils;
Popper.placements = placements;
Popper.Defaults = Defaults;

export default Popper;
//# sourceMappingURL=popper.js.map