Creating a counter component

<!doctype html>
<html>
  <head>
    <base href=".">
    <title>Angular + TypeScript</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>
    <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>
    <app-root>
      Loading...
    </app-root>
  </body>
</html>

/* Styles go here */

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'
    }
  }
});

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

platformBrowserDynamic().bootstrapModule(AppModule);

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  styles: [`
    .app {
      display: block;
      text-align: center;
      padding: 25px;
      background: #f5f5f5;
    }
  `],
  template: `
    <div class="app">
      <counter></counter>
    </div>
  `
})
export class AppComponent {}

import { Component } from '@angular/core';

@Component({
  selector: 'counter',
  styles: [`
    .counter {
      position: relative;
    }
    .counter__input {
      border: 0;
      border-radius: 3px;
      height: 30px;
      max-width: 100px;
      text-align: center;
    }
    .counter__button {
      outline: 0;
      cursor: pointer;
      height: 30px;
      width: 30px;
      border: 0;
      border-radius: 3px;
      background: #0088cc;
      color: #fff;
    }
  `],
  template: `
    <div class="counter">
      <div class="counter__container">
        <button (click)="decrement();" class="counter__button">
          -
        </button>
        <input type="text" class="counter__input" [value]="counterValue">
        <button (click)="increment();" class="counter__button">
          +
        </button>
      </div>
    </div>
  `
})
export class CounterComponent {
  counterValue: number = 0;
  increment() {
    this.counterValue++;
  }
  decrement() {
    this.counterValue--;
  }
}

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { CounterComponent } from './counter.component.ts';

import { AppComponent } from './app.component.ts';

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