Angular2 + Typescript Handling events using rxjs

<!DOCTYPE html>
<html>

  <head>
    <base href="." />
    <title>angular2 playground</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://unpkg.com/zone.js/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js/dist/long-stack-trace-zone.js"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script>
    <script src="https://unpkg.com/systemjs@0.19.31/dist/system.js"></script>
    <script src="config.js"></script>
    <script>
    System.import('app')
      .catch(console.error.bind(console));
  </script>
  </head>

  <body>
    <my-app>
    loading...
  </my-app>
  </body>

</html>

/* Styles go here */

### Handling forms events in Angular2

An alternative to handle forms events using rxjs but keeping template free of javascript code

Licence: MIT

System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  paths: {
    'npm:': 'https://unpkg.com/'
  },
  //map tells the System loader where to look for things
  map: {
    
    'app': './src',
    
    '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
    '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
    '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
    '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
    '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
    '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
    '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
    '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',
    
    '@angular/core/testing': 'npm:@angular/core/bundles/core-testing.umd.js',
    '@angular/common/testing': 'npm:@angular/common/bundles/common-testing.umd.js',
    '@angular/compiler/testing': 'npm:@angular/compiler/bundles/compiler-testing.umd.js',
    '@angular/platform-browser/testing': 'npm:@angular/platform-browser/bundles/platform-browser-testing.umd.js',
    '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic-testing.umd.js',
    '@angular/http/testing': 'npm:@angular/http/bundles/http-testing.umd.js',
    '@angular/router/testing': 'npm:@angular/router/bundles/router-testing.umd.js',
    
    'rxjs': 'npm:rxjs',
    'typescript': 'npm:typescript@2.0.2/lib/typescript.js'
  },
  //packages defines our app package
  packages: {
    app: {
      main: './main.ts',
      defaultExtension: 'ts'
    },
    rxjs: {
      defaultExtension: 'js'
    }
  }
});

//main entry point
import {platformBrowserDynamic} from '@angular/platform-browser-dynamic';
import {AppModule} from './app';

platformBrowserDynamic().bootstrapModule(AppModule)

import {Component, NgModule, ViewChild, AfterViewInit} from '@angular/core';
import {BrowserModule} from '@angular/platform-browser';
import {Observable} from 'rxjs/Observable';
import {Subject} from 'rxjs/Subject';
import 'rxjs/add/observable/fromEvent';
import 'rxjs/add/operator/filter';
import 'rxjs/add/operator/merge';

@Component({
  selector: 'my-app',
  template: `
      <h1>Handling Forms events in Angular2 @Component</h1>
      
      <p>No Javascript code in the button</p>
      <button #click>Click count {{counter}}</button>
      
      <p>Javascript code in this button</p>
      <p><i>Too much code in my opinion</i></p>
      <button (click)="buttonClick$.next()">Click count {{counter}}</button>
      <hr>
      <div class="mouseover">
        <p>Parent / Child events: {{overElementText}}</p>
        <p><i>Move mouse over items</i></p>
        <ul #mouseOver>
          <li>element 1</li>
          <li>element 2</li>
          <li>element n</li>
        </ul>
      </div>
  `
})
export class App {
  click$: Observable<any>;
  mouseOver$: Observable<MouseEvent>;
  buttonClick$: Subject<any> =  new Subject();
  
  counter: number = 0;
  overElementText: string;

  @ViewChild('click') click: any;
  @ViewChild('mouseOver') mouseOver: any;
  
  constructor() {}
  
  ngAfterViewInit() :void {
    const clickButton = this.click.nativeElement;
    this.click$ = Observable.fromEvent(clickButton, 'click');
    this.click$
      .merge(this.buttonClick$)
      .subscribe(()=> this.counter++));
    const mouseOver = this.mouseOver.nativeElement;
    this.mouseOver$ = Observable.fromEvent(mouseOver, 'mouseover');
    this.mouseOver$
      .filter(e => e.fromElement.parentElement === mouseOver)
      .subscribe(this.overParentEventHandler.bind(this));
  }
  
  overParentEventHandler(event : MouseEvent) :void {
    const target = event.fromElement;
    this.overElementText = target && target.innerText || '';
  }
}

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}