share

signature: share(): Observable

Share source among multiple subscribers.

💡 share is like multicast with a Subject and refCount!

Ultimate RxJS

Examples

Example 1: Multiple subscribers sharing source

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { timer } from 'rxjs';
import { tap, mapTo, share } from '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));

Additional Resources

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