Angular Classic data flow between components

<!DOCTYPE html>
<html>

  <head>
    <base href="." />
    <script type="text/javascript" charset="utf-8">
      window.AngularVersionForThisPlunker = '4.3.0'
    </script>
    <title>angular playground</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@0.8.12/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js@0.8.12/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 */

### Angular Starter Plunker - Typescript

var angularVersion;
if(window.AngularVersionForThisPlunker === 'latest'){
  angularVersion = ''; //picks up latest
}
else {
  angularVersion = '@' + window.AngularVersionForThisPlunker;
}

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'+ angularVersion + '/bundles/core.umd.js',
    '@angular/common': 'npm:@angular/common' + angularVersion + '/bundles/common.umd.js',
    '@angular/compiler': 'npm:@angular/compiler' + angularVersion  + '/bundles/compiler.umd.js',
    '@angular/platform-browser': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser.umd.js',
    '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic.umd.js',
    '@angular/http': 'npm:@angular/http' + angularVersion + '/bundles/http.umd.js',
    '@angular/router': 'npm:@angular/router' + angularVersion +'/bundles/router.umd.js',
    '@angular/forms': 'npm:@angular/forms' + angularVersion + '/bundles/forms.umd.js',
    '@angular/animations': 'npm:@angular/animations' + angularVersion + '/bundles/animations.umd.js',
    '@angular/platform-browser/animations': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-animations.umd.js',
    '@angular/animations/browser': 'npm:@angular/animations' + angularVersion + '/bundles/animations-browser.umd.js',
    
    '@angular/core/testing': 'npm:@angular/core' + angularVersion + '/bundles/core-testing.umd.js',
    '@angular/common/testing': 'npm:@angular/common' + angularVersion + '/bundles/common-testing.umd.js',
    '@angular/compiler/testing': 'npm:@angular/compiler' + angularVersion + '/bundles/compiler-testing.umd.js',
    '@angular/platform-browser/testing': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-testing.umd.js',
    '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic-testing.umd.js',
    '@angular/http/testing': 'npm:@angular/http' + angularVersion + '/bundles/http-testing.umd.js',
    '@angular/router/testing': 'npm:@angular/router' + angularVersion + '/bundles/router-testing.umd.js',
    'tslib': 'npm:tslib@1.6.1',
    'rxjs': 'npm:rxjs@5.4.2',
    'typescript': 'npm:typescript@2.2.1/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)

//our root app component
import {Component, NgModule, VERSION, ViewChild} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser'
import {FirstComponent} from './first.component'
import {SecondComponent} from './second.component'

@Component({
  selector: 'my-app',
  template: `
    <first-component (messageSent)="onMessageSentFromFirst($event)"></first-component>
    <br/>
    <second-component [dataReceived]="messages" [isChanged]="isChanged"></second-component>
    <br/>
  `,
})
export class App {
  public messages:any = [];
  private isChanged:boolean;
  
  public onMessageSentFromFirst(event : any) {
    this.messages.push(event);
    this.isChanged = !this.isChanged;
  }
}

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

import {Component, Input} from '@angular/core'

@Component({
  selector: 'second-component',
  template: '<h1>Second Component (Receiver)</h1><div *ngFor="let data of dataReceived">{{data}}</div>'
})
export class SecondComponent {
  @Input()
    private dataReceived : Array<string>;
    private dataReceivedLength = 0;
  
    @Input()
    public isChanged:boolean;

  
  ngOnChanges(data:any) {
    if(data.isChanged) {
      this.onMessageReceived(this.dataReceived[this.dataReceived.length-1]);
    }  
  }
  
  ngDoCheck() {
    if(this.dataReceived.length != this.dataReceivedLength) {
      this.dataReceivedLength = this.dataReceived.length;
      this.onMessageReceived(this.dataReceived[this.dataReceived.length-1]);
    }
  }
  
  public onMessageReceived(message : string) {
	  // Perform actions
  }
}

import {Component, EventEmitter, Output} from '@angular/core'

@Component({
  selector: 'first-component',
  template: '<h1>First Component (Sender)</h1><button (click)="onClick()">Send to components</button>'
})
export class FirstComponent {
  @Output('messageSent') messageSent = new EventEmitter<string>();
  
  onClick() {
    this.messageSent.emit("Sent from First Component");
  }
}