@atlassian/aui/src/js/aui/polyfills/custom-event.js

Atlassian User Interface library

let CustomEvent;

(function () {
    if (window.CustomEvent) {
        // Some browsers don't support constructable custom events yet.
        try {
            const ce = new window.CustomEvent('name', {
                bubbles: false,
                cancelable: true,
                detail: {
                    x: 'y'
                }
            });
            ce.preventDefault();
            if (ce.defaultPrevented !== true) {
                throw new Error('Could not prevent default');
            }
            if (ce.type !== 'name') {
                throw new Error('Could not set custom name');
            }
            if (ce.detail.x !== 'y') {
                throw new Error('Could not set detail');
            }

            CustomEvent = window.CustomEvent;
            return;
        } catch (e) {
            // polyfill it
        }
    }

    /**
     * @type CustomEvent
     * @param {String} event - the name of the event.
     * @param {Object} [params] - optional configuration of the custom event.
     * @param {Boolean} [params.cancelable=false] - A boolean indicating whether the event is cancelable (i.e., can call preventDefault and set the defaultPrevented property).
     * @param {Boolean} [params.bubbles=false] - A boolean indicating whether the event bubbles up through the DOM or not.
     * @param {Boolean} [params.detail] - The data passed when initializing the event.
     * @extends Event
     * @returns {Event}
     * @constructor
     */
    CustomEvent = function(event, params) {
        params = params || {bubbles: false, cancelable: false, detail: undefined};

        var evt = document.createEvent('CustomEvent');

        evt.initCustomEvent(event, !!params.bubbles, !!params.cancelable, params.detail);
        var origPrevent = evt.preventDefault;
        evt.preventDefault = function () {
            origPrevent.call(this);
            try {
                Object.defineProperty(this, 'defaultPrevented', {
                    get: function () {
                        return true;
                    }
                });
            } catch (e) {
                if (!this.defaultPrevented) {
                    this.defaultPrevented = true;
                }
            }
        };

        return evt;
    }

    CustomEvent.prototype = window.Event.prototype;
}());

export default CustomEvent;