Question

reduce

函数签名: reduce(accumulator: function, seed: any): Observable

将源 observalbe 的值归并为单个值，当源 observable 完成时将这个值发出。

类似于 Array.prototype.reduce()

如果每次发送时都需要当前的累加值，请使用 scan!

示例

示例 1: 数字流的加和

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { of } from 'rxjs';
import { reduce } from 'rxjs/operators';

const source = of(1, 2, 3, 4);
const example = source.pipe(reduce((acc, val) => acc + val));
// 输出: Sum: 10'
const subscribe = example.subscribe(val => console.log('Sum:', val));

其他资源

• reduce :newspaper: - 官方文档
• scan() vs reduce() | RxJS 教程 :video_camera: - Academind

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源码: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/reduce.ts