create

signature: create(subscribe: function)

Create an observable with given subscription function.

Examples

Example 1: Observable that emits multiple values

( jsBin |
jsFiddle )

import { Observable } from 'rxjs/Observable';
/*
  Create an observable that emits 'Hello' and 'World' on  
  subscription.
*/
const hello = Observable.create(function(observer) {
  observer.next('Hello');
  observer.next('World');
});
//output: 'Hello'...'World'
const subscribe = hello.subscribe(val => console.log(val));

Example 2: Observable that emits even numbers on timer

( jsBin |
jsFiddle )

import { Observable } from 'rxjs/Observable';
/*
  Increment value every 1s, emit even numbers.
*/
const evenNumbers = Observable.create(function(observer) {
  let value = 0;
  const interval = setInterval(() => {
    if (value % 2 === 0) {
      observer.next(value);
    }
    value++;
  }, 1000);
  return () => clearInterval(interval);
});
//output: 0...2...4...6...8
const subscribe = evenNumbers.subscribe(val => console.log(val));
//unsubscribe after 10 seconds
setTimeout(() => {
  subscribe.unsubscribe();
}, 10000);

Additional Resources

• create
  - Official docs
• Creation operators: Create()
  - André Staltz
• Using Observable.create for fine-grained control
  - Shane Osbourne

Source Code:
https://github.com/ReactiveX/rxjs/blob/master/src/internal/observable/GenerateObservable.ts