do
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2023-12-01
do / tap
函数签名: do(nextOrObserver: function, error: function, complete: function): Observable
Transparently perform actions or side-effects, such as logging.
透明地执行操作或副作用,比如打印日志。
If you are using as a pipeable operator, do
is known as tap
!
示例
示例 1: 使用 do 输出日志
( StackBlitz | jsBin | jsFiddle )
// RxJS v6+
import { of } from 'rxjs';
import { tap, map } from 'rxjs/operators';
const source = of(1, 2, 3, 4, 5);
// 使用 tap 透明地打印 source 中的值
const example = source.pipe(
tap(val => console.log(`BEFORE MAP: ${val}`)),
map(val => val + 10),
tap(val => console.log(`AFTER MAP: ${val}`))
);
// 'tap' 并不转换值
// 输出: 11...12...13...14...15
const subscribe = example.subscribe(val => console.log(val));
其他资源
- do :newspaper: - 官方文档
- 使用 do 打印流 :video_camera: :dollar: - John Linquist
- 工具操作符: do :video_camera: :dollar: - André Staltz
源码: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/do.ts