82 lines
2.8 KiB
JavaScript
82 lines
2.8 KiB
JavaScript
|
import { Subscriber } from '../Subscriber';
|
||
|
|
/**
|
||
|
|
* 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.
|
||
|
|
*
|
||
|
|
* <span class="informal">Takes values from the source only while they pass the
|
||
|
|
* condition given. When the first value does not satisfy, it completes.</span>
|
||
|
|
*
|
||
|
|
* <img src="./img/takeWhile.png" width="100%">
|
||
|
|
*
|
||
|
|
* `takeWhile` subscribes and begins mirroring the source Observable. Each value
|
||
|
|
* emitted on the source is given to the `predicate` function which returns a
|
||
|
|
* boolean, representing a condition to be satisfied by the source values. The
|
||
|
|
* output Observable emits the source values until such time as the `predicate`
|
||
|
|
* returns false, at which point `takeWhile` stops mirroring the source
|
||
|
|
* Observable and completes the output Observable.
|
||
|
|
*
|
||
|
|
* @example <caption>Emit click events only while the clientX property is greater than 200</caption>
|
||
|
|
* var clicks = Rx.Observable.fromEvent(document, 'click');
|
||
|
|
* var result = clicks.takeWhile(ev => ev.clientX > 200);
|
||
|
|
* result.subscribe(x => console.log(x));
|
||
|
|
*
|
||
|
|
* @see {@link take}
|
||
|
|
* @see {@link takeLast}
|
||
|
|
* @see {@link takeUntil}
|
||
|
|
* @see {@link skip}
|
||
|
|
*
|
||
|
|
* @param {function(value: T, index: number): boolean} 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.
|
||
|
|
* @return {Observable<T>} An Observable that emits the values from the source
|
||
|
|
* Observable so long as each value satisfies the condition defined by the
|
||
|
|
* `predicate`, then completes.
|
||
|
|
* @method takeWhile
|
||
|
|
* @owner Observable
|
||
|
|
*/
|
||
|
|
export function takeWhile(predicate) {
|
||
|
|
return (source) => source.lift(new TakeWhileOperator(predicate));
|
||
|
|
}
|
||
|
|
class TakeWhileOperator {
|
||
|
|
constructor(predicate) {
|
||
|
|
this.predicate = predicate;
|
||
|
|
}
|
||
|
|
call(subscriber, source) {
|
||
|
|
return source.subscribe(new TakeWhileSubscriber(subscriber, this.predicate));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
/**
|
||
|
|
* We need this JSDoc comment for affecting ESDoc.
|
||
|
|
* @ignore
|
||
|
|
* @extends {Ignored}
|
||
|
|
*/
|
||
|
|
class TakeWhileSubscriber extends Subscriber {
|
||
|
|
constructor(destination, predicate) {
|
||
|
|
super(destination);
|
||
|
|
this.predicate = predicate;
|
||
|
|
this.index = 0;
|
||
|
|
}
|
||
|
|
_next(value) {
|
||
|
|
const destination = this.destination;
|
||
|
|
let result;
|
||
|
|
try {
|
||
|
|
result = this.predicate(value, this.index++);
|
||
|
|
}
|
||
|
|
catch (err) {
|
||
|
|
destination.error(err);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
this.nextOrComplete(value, result);
|
||
|
|
}
|
||
|
|
nextOrComplete(value, predicateResult) {
|
||
|
|
const destination = this.destination;
|
||
|
|
if (Boolean(predicateResult)) {
|
||
|
|
destination.next(value);
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
destination.complete();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
//# sourceMappingURL=takeWhile.js.map
|