CODE EXAMPLE FOR JAVASCRIPT

angular wait all subscriptions

// Concat 
let first = Observable.timer(10,500).map(r => {
  return {source:1,value:r};
}).take(4);
let second = Observable.timer(10,500).map(r => {
  return {source:2,value:r};
}).take(4);
first.concat(second).subscribe(res => this.concatStream.push(res));
// This will merge the two but you will receive the first observable result before the second:
// 0 1 2 3 0 1 2 3

// Merge
let first = Observable.timer(10,500).map(r => {
  return {source:1,value:r};
}).take(4);
let second = Observable.timer(10,500).map(r => {
  return {source:2,value:r};
}).take(4);
first.merge(second).subscribe(res => this.mergeStream.push(res));

// You will get:
// 0 0 1 1 2 2 3 3

// Fork Join
let first = Observable.of({source:1,value:1});
let second = Observable.of({source:2,value:1});
Observable.forkJoin(first,second).subscribe((res:Array) => this.forkJoinStream = res);

// FlatMap
let first = Observable.of(10);
first.flatMap((operand1) => {
  return Observable.of(operand1 + 10);
})
.subscribe(res => this.flatMappedStreams = {msg: '10 + 10 = ' + res});