react-native-blob-util/polyfill/EventTarget.js

A module provides upload, download, and files access API. Supports file stream read/write for process large files.

// Copyright 2016 wkh237@github. All rights reserved.
// Use of this source code is governed by a MIT-style license that can be
// found in the LICENSE file.

import Log from '../utils/log.js';

const log = new Log('EventTarget');

log.disable();

export default class EventTarget {

    listeners: any;

    constructor() {
        log.info('constructor called');
        this.listeners = {};
    }

    /**
     * Add an event listener to given event type
     * @param {string} type Event type string
     * @param {(Event) => void} cb   Event handler function
     */
    addEventListener(type: string, cb: () => void) {
        log.info('add event listener', type, cb);
        if (!(type in this.listeners)) {
            this.listeners[type] = [];
        }
        this.listeners[type].push(cb);
    }

    /**
     * Remove an event listener
     * @param  {string} type Type of the event listener
     * @param  {()=>void} cb Event listener function.
     * @return {[type]}             [description]
     */
    removeEventListener(type: string, cb: () => void) {
        log.info('remove event listener', type, cb);
        if (!(type in this.listeners))
            return;
        let handlers = this.listeners[type];
        for (let i in handlers) {
            if (cb === handlers[i]) {
                handlers.splice(i, 1);
                return this.removeEventListener(type, cb);
            }
        }
    }

    /**
     * Dispatch an event
     * @param {string} type Event type.
     * @param {Event} event Event data payload.
     */
    dispatchEvent(type: string, event: Event) {
        log.info('dispatch event', event);
        if (!(type in this.listeners))
            return;
        let handlers = this.listeners[type];
        for (let i in handlers) {
            handlers[i].call(this, event);
        }

    }

    /**
     * Remove all registered listeners from this object.
     * @nonstandard
     * @return {[type]} [description]
     */
    clearEventListeners() {
        for (let i in this.listeners) {
            delete this.listeners[i];
        }
    }

}