ngOnChanges Example

<!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>
    <sample-app>loading...</sample-app>
  </body>

</html>

/* Styles go here */

### Angular Example: OnChanges
## Example App

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/app.module';

platformBrowserDynamic().bootstrapModule(AppModule);

//our root app component
import { Component, NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { PropInputBindComponent } from './prop-input-bind/prop-input-bind.component.ts';
import { NoneInputBindComponent } from './none-input-bind/none-input-bind.component.ts';

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

import { Component } from '@angular/core';
import { TempData } from './temp-data/temp-data.model.ts';

@Component({
  selector: 'sample-app',
  template: `
  <h2>OnChanges</h2>
  myNum: <input type="number" [(ngModel)]="numVal" /> <br>
  myStr: <input type="text" [(ngModel)]="strVal" /> <br>
  temp.id: <input type="number" [(ngModel)]="temp.id" /> <br>
  temp.content: <input type="text" [(ngModel)]="temp.content" /> <br>
  <prop-input-bind [myNum]="numVal" [myStr]="strVal" [tempData]="temp">
  </prop-input-bind>
  <none-input-bind></none-input-bind>
  `,
})
export class AppComponent {
  numVal: number;
  strVal: string;
  temp: TempData;
  
  constructor() { 
    this.numVal = 1;
    this.strVal = 'test'
    this.temp = new TempData(10, 'sample data')
  }
}

import { Component, Input, OnChanges, SimpleChanges } from '@angular/core';
import { TempData } from '../temp-data/temp-data.model.ts';

@Component({
  selector: 'prop-input-bind',
  template: `
  <h4>PropInputBindComponent</h4>
  <p>myNum: {{myNum}}</p>
  <p>myStr: {{myStr}}</p>
  <p>tempData.content</p>
  `,
})
export class PropInputBindComponent implements OnChanges {
  @Input() myNum: number;
  @Input() myStr: string;
  @Input() tempData: TempData;
  
  constructor() { ;

  }
  
  ngOnChanges(changes: SimpleChanges) {
    if(changes.myNum && !changes.myNum.isFirstChange()) {
      // exteranl API call or more preprocessing...
    }
    
    for (let propName in changes) {
      let change = changes[propName];
      console.dir(change);
      if(change.isFirstChange()) {
        console.log(`first change: ${propName}`);
      } else {
        console.log(`prev: ${change.previousValue}, cur: ${change.currentValue}`);
      }
    }
  }
}

export class TempData {
  id: number;
  content: string;
  subData: SubObj;
  
  constructor(_id: number, _content: string) {
    this.id = _id;
    this.content = _content;
    this.subData = new SubObj(this.id + 100, 'data...');
  }
}

export class SubObj {
  data1: number;
  data2: string;
  
  constructor(d1: number, d2: string) {
    this.data1 = d1;
    this.data2 = d2;
  }
}

import { Component, OnChanges, SimpleChanges } from '@angular/core';

@Component({
  selector: 'none-input-bind',
  template: `
  <h4>NoneInputBindComponent</h4>
  `,
})
export class NoneInputBindComponent implements OnChanges {

  constructor() { ;

  }
  
  ngOnChanges(changes: SimpleChanges) {
    
  }
}