Question

expand

函数签名: expand(project: function, concurrent: number, scheduler: Scheduler): Observable

递归调用提供的函数

示例

示例 1: 每次调用加1

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval, of } from 'rxjs';
import { expand, take } from 'rxjs/operators';

// 发出 2
const source = of(2);
const example = source.pipe(
  // 递归调用提供的函数
  expand(val => {
    // 2,3,4,5,6
    console.log(`Passed value: ${val}`);
    // 3,4,5,6
    return of(1 + val);
  }),
  // 用5次
  take(5)
);
/*
    "RESULT: 2"
    "Passed value: 2"
    "RESULT: 3"
    "Passed value: 3"
    "RESULT: 4"
    "Passed value: 4"
    "RESULT: 5"
    "Passed value: 5"
    "RESULT: 6"
    "Passed value: 6"
*/
// 输出: 2,3,4,5,6
const subscribe = example.subscribe(val => console.log(`RESULT: ${val}`));

相关食谱

• 游戏循环

其他资源

• expand :newspaper: - 官方文档

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