RxJS takeWhile

只要每個值滿足給定值，就發(fā)出源 Observable 發(fā)出的值predicate，然后在predicate不滿足要求時立即完成。

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

參量

returns

MonoTypeOperatorFunction<T>：一個 Observable，它從源 Observable 發(fā)出值，只要每個值都滿足定義的條件 predicate，然后完成。

描述

僅在它們通過給定條件時才從源中獲取值。當(dāng)?shù)谝粋€值不滿足時，它完成。

takeWhile訂閱并開始鏡像源 Observable。源上發(fā)出的每個值都被提供給predicate函數(shù)，該函數(shù)返回一個布爾值，表示源值要滿足的條件。輸出 Observable 會發(fā)出源值，直到predicate 返回false為止，此時將takeWhile停止鏡像源 Observable 并完成輸出 Observable。

例

僅當(dāng) clientX 屬性大于 200 時才發(fā)出點擊事件

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));

超載

takeWhile(predicate: (value: T, index: number) => value is S): OperatorFunction<T, S>

returnsOperatorFunction<T, S>

takeWhile(predicate: (value: T, index: number) => value is S, inclusive: false): OperatorFunction<T, S>

returnsOperatorFunction<T, S>

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

returnsMonoTypeOperatorFunction<T> |

也可以看看

• take
• takeLast
• takeUntil
• skip