TakeWhile

Emits values emitted by the source Observable so long as each value satisfies the given predicate, and then completes as soon as this predicate is not satisfied.

Syntax

takeWhile<T>(predicate: (value: T, index: number) => boolean, inclusive: boolean = false): MonoTypeOperatorFunction<T>

Parameters	Description
predicate	A function that evaluates a value emitted by the source Observable and returns a boolean. Also takes the (zero-based) index as the second argument.
inclusive optional	Default is false. When set to true the value that caused predicate to return false will also be emitted.

Returns

MonoTypeOperatorFunction: A function that returns an Observable that emits values from the source Observable so long as each value satisfies the condition defined by the predicate, then completes.

Example

Emit click events only while the clientX property is greater than 200

import { fromEvent } from 'rxjs';
import { takeWhile } from 'rxjs/operators';

const clicks = fromEvent(document, 'click');
const result = clicks.pipe(takeWhile(ev => ev.clientX > 200));
result.subscribe(x => console.log(x));