find.md

find

signature: find(predicate: function)

Emit the first item that passes predicate then complete.

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💡 If you always want the first item emitted, regardless of condition, try first()!

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Examples

Example 1: Find click inside box, repeat when a click occurs outside of box

( StackBlitz)

// RxJS v6+
import { fromEvent } from 'rxjs';
import { find, repeatWhen, mapTo, startWith, filter } from 'rxjs/operators';

// elem ref
const status = document.getElementById('status');

// streams
const clicks$ = fromEvent(document, 'click');

clicks$
  .pipe(
    find((event: any) => event.target.id === 'box'),
    mapTo('Found!'),
    startWith('Find me!'),
    // reset when click outside box
    repeatWhen(() =>
      clicks$.pipe(filter((event: any) => event.target.id !== 'box'))
    )
  )
  .subscribe(message => (status.innerHTML = message));

Additional Resources

• find 📰 - Official docs

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