app.ts

app.ts

import {Component, NgModule, VERSION} from '@angular/core'
import {Http} from '@angular/http'// DON'T FORGOT TO IMPORT HTTP 
import {BrowserModule} from '@angular/platform-browser'
import {HttpModule} from '@angular/http'; // DON'T FORGOT TO IMPORT HTTPMODULE

@Component({
  selector: 'my-app',
  template: 
   `<div>
     <h2>Response from server: {{greeting}}</h2>
    </div>`
})

export class App {
  greeting:string;
  
  constructor(protected http: Http) {
      this.requestGreeting()
  }
  
  requestGreeting() {
    this.http.get("https://private-8ace8-helloworld409.apiary-mock.com/greeting").subscribe(res => {
      this.greeting = res.json().data;
    })
  }
}

@NgModule({
  imports: [ BrowserModule, HttpModule ], // DON'T FORGOT TO IMPORT HTTPMODULE
  declarations: [ App ],
  bootstrap: [ App ]
})

export class AppModule {}