share

signature: share(): Observable

Share source among multiple subscribers.

share is like multicast with a Subject and refCount!

Examples

Example 1: Multiple subscribers sharing source

( jsBin |
jsFiddle )

import { timer } from 'rxjs/observable/timer';
import { tap, mapTo, share } 'rxjs/operators';
//emit value in 1s
const source = timer(1000);
//log side effect, emit result
const example = source.pipe(
  tap(() => console.log('***SIDE EFFECT***')),
  mapTo('***RESULT***')
);
/*
  ***NOT SHARED, SIDE EFFECT WILL BE EXECUTED TWICE***
  output:
  "***SIDE EFFECT***"
  "***RESULT***"
  "***SIDE EFFECT***"
  "***RESULT***"
*/
const subscribe = example.subscribe(val => console.log(val));
const subscribeTwo = example.subscribe(val => console.log(val));
//share observable among subscribers
const sharedExample = example.pipe(share());
/*
  ***SHARED, SIDE EFFECT EXECUTED ONCE***
  output:
  "***SIDE EFFECT***"
  "***RESULT***"
  "***RESULT***"
*/
const subscribeThree = sharedExample.subscribe(val => console.log(val));
const subscribeFour = sharedExample.subscribe(val => console.log(val));

Related Recipes

• Progress Bar
• Game Loop

Additional Resources

• share
  - Official docs
• Sharing streams with share
  - John Linquist

Source Code:
https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/share.ts