noVNC/core/util/eventtarget.js

/*
 * noVNC: HTML5 VNC client
 * Copyright (C) 2019 The noVNC Authors
 * Licensed under MPL 2.0 (see LICENSE.txt)
 *
 * See README.md for usage and integration instructions.
 */

export default class EventTargetMixin {
    constructor() {
        this._listeners = new Map();
    }

    addEventListener(type, callback) {
        if (!this._listeners.has(type)) {
            this._listeners.set(type, new Set());
        }
        this._listeners.get(type).add(callback);
    }

    removeEventListener(type, callback) {
        if (this._listeners.has(type)) {
            this._listeners.get(type).delete(callback);
        }
    }

    dispatchEvent(event) {
        if (!this._listeners.has(event.type)) {
            return true;
        }
        this._listeners.get(event.type)
            .forEach(callback => callback.call(this, event));
        return !event.defaultPrevented;
    }
}