Function Popper

static/bootstrap4/js/bootstrap.bundle.js:3974–4038

* 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 t

(reference, popper)

     * @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;