const source = Rx.Observable.of('Hello');
//map to inner observable and flatten
const example = source.mergeMap(val => Rx.Observable.of(`${val} World!`));

const subscribe = example.subscribe(val => console.log(val)); //output: 'Hello World!'

const getPostOne$ = Rx.Observable.timer(1000).mapTo({id: 1});
const getPostTwo$ = Rx.Observable.timer(2000).mapTo({id: 2});

Rx.Observable.forkJoin(getPostOne$, getPostTwo$).subscribe(
 res => console.log(res) // [{id: 1}, {id: 2}]
); 

import { Component, OnInit } from '@angular/core';
import { Http } from '@angular/http';

import 'rxjs/add/operator/map';

@Component({
 selector: 'app-root',
 template: `
  <p>HttpModule Demo</p>
 `
})
export class AppComponent implements OnInit {
 constructor(private http: Http) { }

 ngOnInit() {
  this.http.get('https://jsonplaceholder.typicode.com/users')
   .map(res => res.json())
   .subscribe(users => console.log(users));
 }
}

import { Component, OnInit } from '@angular/core';
import { Http } from '@angular/http';
import 'rxjs/add/operator/map';

@Component({
 selector: 'app-root',
 template: `
  <p>{{username}} Detail Info</p>
  {{user | json}}
 `
})
export class AppComponent implements OnInit {
 constructor(private http: Http) { }

 apiUrl = 'https://jsonplaceholder.typicode.com/users';
 username: string = '';
 user: any;

 ngOnInit() {
  this.http.get(this.apiUrl)
   .map(res => res.json())
   .subscribe(users => {
    let username = users[6].username;
    this.http.get(`${this.apiUrl}?username=${username}`)
     .map(res => res.json())
     .subscribe(
      user => {
       this.username = username;
       this.user = user;
      });
   });
 }
}

import { Component, OnInit } from '@angular/core';
import { Http } from '@angular/http';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/mergeMap';

@Component({
 selector: 'app-root',
 template: `
  <p>{{username}} Detail Info</p>
  {{user | json}}
 `
})
export class AppComponent implements OnInit {
 constructor(private http: Http) { }

 apiUrl = 'https://jsonplaceholder.typicode.com/users';

 username: string = '';

 user: any;

 ngOnInit() {
  this.http.get(this.apiUrl)
   .map(res => res.json())
   .mergeMap(users => {
    this.username = users[6].username;
    return this.http.get(`${this.apiUrl}?username=${this.username}`)
     .map(res => res.json())
   })
   .subscribe(user => this.user = user);
 }
}

import { Component, OnInit } from '@angular/core';
import { Http } from '@angular/http';

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map';
import 'rxjs/add/observable/forkJoin';

@Component({
 selector: 'app-root',
 template: `
  <p>Post Detail Info</p>
  <ul>
   <li>{{post1 | json}}</li>
   <li>{{post2 | json}}</li>
  </ul>
 `
})
export class AppComponent implements OnInit {
 constructor(private http: Http) { }

 apiUrl = 'https://jsonplaceholder.typicode.com/posts';

 post1: any;

 post2: any;

 ngOnInit() {
  let post1 = this.http.get(`${this.apiUrl}/1`);
  let post2 = this.http.get(`${this.apiUrl}/2`);

  Observable.forkJoin([post1, post2])
   .subscribe(results => {
    this.post1 = results[0];
    this.post2 = results[1];
   });
 }
}

var source = Rx.Observable.fromEvent(document.body, 'click');
var example = source.switchMap(e => Rx.Observable.interval(100).take(3));

example.subscribe({
  next: (value) => { console.log(value); },
  error: (err) => { console.log('Error: ' + err); },
  complete: () => { console.log('complete'); }
});

source : -----------c--c-----------------...
    concatMap(c => Rx.Observable.interval(100).take(3))
example: -------------0--0-1-2-----------...