bootstrap.bundle.js

        case '%':
        case '%r':
        default:
          element = referenceOffsets;
      }

      var 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
      var size = void 0;
      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) {
    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$1(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,
        _data$offsets = data.offsets,
        popper = _data$offsets.popper,
        reference = _data$offsets.reference;

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

    var offsets = void 0;
    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,
        left = popperStyles.left,
        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 value = popper[placement];
        if (popper[placement] < boundaries[placement] && !options.escapeWithReference) {
          value = Math.max(popper[placement], boundaries[placement]);
        }
        return defineProperty({}, placement, value);
      },
      secondary: function secondary(placement) {
        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 defineProperty({}, mainSide, value);
      }
    };

    order.forEach(function (placement) {
      var 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) {
    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 _data$offsets = data.offsets,
          reference = _data$offsets.reference,
          popper = _data$offsets.popper;

      var isVertical = ['bottom', 'top'].indexOf(basePlacement) !== -1;
      var side = isVertical ? 'left' : 'top';
      var measurement = isVertical ? 'width' : 'height';

      var shiftOffsets = {
        start: defineProperty({}, side, reference[side]),
        end: defineProperty({}, 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;
    }

    var refRect = data.offsets.reference;
    var bound = find$1(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 _data$offsets = data.offsets,
        popper = _data$offsets.popper,
        reference = _data$offsets.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.<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 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.<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%'
     * ```
     * > **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.<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 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.<br />
   * These can be overridden using the `options` argument of Popper.js.<br />
   * 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.<br />
     * By default, it is set to no-op.<br />
     * Access Popper.js instance with `data.instance`.
     * @prop {onCreate}
     */
    onCreate: function 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, it is set to no-op.<br />
     * Access Popper.js instance with `data.instance`.
     * @prop {onUpdate}
     */
    onUpdate: function 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: modifiers
  };

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

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

  // Utils
  // Methods
  var Popper = function () {
    /**
     * Creates a new Popper.js instance.
     * @class Popper
     * @param {Element|referenceObject} reference - The reference element used to position the popper
     * @param {Element} popper - The HTML / XML element used as the popper
     * @param {Object} options - Your custom options to override the ones defined in [Defaults](#defaults)
     * @return {Object} instance - The generated Popper.js instance
     */
    function Popper(reference, popper) {
      var _this = this;

      var options = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : {};
      classCallCheck(this, Popper);

      this.scheduleUpdate = function () {
        return 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 && reference.jquery ? reference[0] : reference;
      this.popper = popper && popper.jquery ? popper[0] : popper;

      // Deep merge modifiers options
      this.options.modifiers = {};
      Object.keys(_extends({}, Popper.Defaults.modifiers, options.modifiers)).forEach(function (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(function (name) {
        return _extends({
          name: name
        }, _this.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.reference, _this.popper, _this.options, modifierOptions, _this.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


    createClass(Popper, [{
      key: 'update',
      value: function update$$1() {
        return update.call(this);
      }
    }, {
      key: 'destroy',
      value: function destroy$$1() {
        return destroy.call(this);
      }
    }, {
      key: 'enableEventListeners',
      value: function enableEventListeners$$1() {
        return enableEventListeners.call(this);
      }
    }, {
      key: 'disableEventListeners',
      value: function disableEventListeners$$1() {
        return disableEventListeners.call(this);
      }

      /**
       * Schedules 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
       */

    }]);
    return 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;

  /**
   * ------------------------------------------------------------------------
   * Constants
   * ------------------------------------------------------------------------
   */

  var NAME$4 = 'dropdown';
  var VERSION$4 = '4.3.1';
  var DATA_KEY$4 = 'bs.dropdown';
  var EVENT_KEY$4 = "." + DATA_KEY$4;
  var DATA_API_KEY$4 = '.data-api';
  var ESCAPE_KEYCODE = 27; // KeyboardEvent.which value for Escape (Esc) key

  var SPACE_KEYCODE = 32; // KeyboardEvent.which value for space key

  var TAB_KEYCODE = 9; // KeyboardEvent.which value for tab key

  var ARROW_UP_KEYCODE = 38; // KeyboardEvent.which value for up arrow key

  var ARROW_DOWN_KEYCODE = 40; // KeyboardEvent.which value for down arrow key

  var RIGHT_MOUSE_BUTTON_WHICH = 3; // MouseEvent.which value for the right button (assuming a right-handed mouse)

  var REGEXP_KEYDOWN = new RegExp(ARROW_UP_KEYCODE + "|" + ARROW_DOWN_KEYCODE + "|" + ESCAPE_KEYCODE);
  var Event$5 = {
    HIDE: "hide" + EVENT_KEY$4,
    HIDDEN: "hidden" + EVENT_KEY$4,
    SHOW: "show" + EVENT_KEY$4,
    SHOWN: "shown" + EVENT_KEY$4,
    CLICK: "click" + EVENT_KEY$4,
    CLICK_DATA_API: "click" + EVENT_KEY$4 + DATA_API_KEY$4,
    KEYDOWN_DATA_API: "keydown" + EVENT_KEY$4 + DATA_API_KEY$4,
    KEYUP_DATA_API: "keyup" + EVENT_KEY$4 + DATA_API_KEY$4
  };
  var ClassName$4 = {
    DISABLED: 'disabled',
    SHOW: 'show',
    DROPUP: 'dropup',
    DROPRIGHT: 'dropright',
    DROPLEFT: 'dropleft',
    MENURIGHT: 'dropdown-menu-right',
    POSITION_STATIC: 'position-static'
  };
  var Selector$4 = {
    DATA_TOGGLE: '[data-toggle="dropdown"]',
    FORM_CHILD: '.dropdown form',
    MENU: '.dropdown-menu',
    NAVBAR_NAV: '.navbar-nav',
    VISIBLE_ITEMS: '.dropdown-menu .dropdown-item:not(.disabled):not(:disabled)'
  };
  var AttachmentMap = {
    TOP: 'top-start',
    TOPEND: 'top-end',
    BOTTOM: 'bottom-start',
    BOTTOMEND: 'bottom-end',
    RIGHT: 'right-start',
    RIGHTEND: 'right-end',
    LEFT: 'left-start',
    LEFTEND: 'left-end'
  };
  var Default$2 = {
    offset: 0,
    flip: true,
    boundary: 'scrollParent',
    reference: 'toggle',
    display: 'dynamic',
    popperConfig: null
  };
  var DefaultType$2 = {
    offset: '(number|string|function)',
    flip: 'boolean',
    boundary: '(string|element)',
    reference: '(string|element)',
    display: 'string',
    popperConfig: '(null|object)'
    /**
     * ------------------------------------------------------------------------
     * Class Definition
     * ------------------------------------------------------------------------
     */

  };

  var Dropdown =
  /*#__PURE__*/
  function () {
    function Dropdown(element, config) {
      this._element = element;
      this._popper = null;
      this._config = this._getConfig(config);
      this._menu = this._getMenuElement();
      this._inNavbar = this._detectNavbar();

      this._addEventListeners();