create

signature: create(subscribe: function)
Create an observable with given subscription function.
​​​​
Examples
Example 1: Observable that emits multiple values
( StackBlitz | jsBin | jsFiddle )
// RxJS v6+
import { Observable } from 'rxjs';
/*
  Create an observable that emits 'Hello' and 'World' on  
  subscription.
*/
const hello = Observable.create(function(observer) {
  observer.next('Hello');
  observer.next('World');
  observer.complete();
});
​
//output: 'Hello'...'World'
const subscribe = hello.subscribe(val => console.log(val));
Example 2: Observable that emits even numbers on timer
( StackBlitz | jsBin | jsFiddle )
// RxJS v6+
import { Observable } from 'rxjs';
​
/*
  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​
ajax
defer
Last updated 1 year ago