remove events/EventEmitter && move Observer to ts

docs/design.md

@@ -5,7 +5,7 @@ design idea is pretty simple :
    - main functionalities are split into several subsystems
    - all subsystems are instantiated by the Hls instance.
    - each subsystem heavily relies on events for internal/external communications.
-   - Events are handled using [EventEmitter](https://nodejs.org/api/events.html)
+   - Events are handled using [EventEmitter3](https://github.com/primus/eventemitter3)
    - bundled for the browser by [webpack](https://webpack.js.org/)
 
 ## Code structure

src/demux/demuxer-worker.js

@@ -7,7 +7,7 @@ import DemuxerInline from '../demux/demuxer-inline';
 import Event from '../events';
 import { enableLogs } from '../utils/logger';
 
-import { EventEmitter } from 'events';
+import { EventEmitter } from 'eventemitter3';
 
 let DemuxerWorker = function (self) {
   // observer setup

src/demux/demuxer.js

@@ -1,4 +1,4 @@
-import { EventEmitter } from 'events';
+import { EventEmitter } from 'eventemitter3';
 import * as work from 'webworkify-webpack';
 
 import Event from '../events';

src/observer.ts

@@ -0,0 +1,15 @@
+import { EventEmitter } from 'eventemitter3';
+
+/**
+ * Simple adapter sub-class of Nodejs-like EventEmitter.
+ */
+export class Observer extends EventEmitter {
+  /**
+   * We simply want to pass along the event-name itself
+   * in every call to a handler, which is the purpose of our `trigger` method
+   * extending the standard API.
+   */
+  trigger (event: string, ...data: Array<any>): void {
+    this.emit(event, event, ...data);
+  }
+}

tests/unit/controller/eme-controller.js

@@ -1,6 +1,6 @@
 import EMEController from '../../../src/controller/eme-controller';
 import HlsMock from '../../mocks/hls.mock';
-import EventEmitter from 'events';
+import { EventEmitter } from 'eventemitter3';
 import { ErrorDetails } from '../../../src/errors';
 
 const sinon = require('sinon');