sample

函数签名: sample(sampler: Observable): Observable

当提供的 observable 发出时从源 observable 中取样。

示例

示例 1: 每2秒对源 observable 取样

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval } from 'rxjs';
import { sample } 'rxjs/operators';

// 每1秒发出值
const source = interval(1000);
// 每2秒对源 observable 最新发出的值进行取样
const example = source.pipe(sample(interval(2000)));
// 输出: 2..4..6..8..
const subscribe = example.subscribe(val => console.log(val));

示例 2: 当 interval 发出时对源 observable 取样

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval, zip, from } from 'rxjs';
import { sample } from 'rxjs/operators';

const source = zip(
  // 发出 'Joe', 'Frank' and 'Bob' in sequence
  from(['Joe', 'Frank', 'Bob']),
  // 每2秒发出值
  interval(2000)
);
// 每2.5秒对源 observable 最新发出的值进行取样
const example = source.pipe(sample(interval(2500)));
// 输出: ["Joe", 0]...["Frank", 1]...........
const subscribe = example.subscribe(val => console.log(val));

示例 3: 区分拖拽和点击

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { fromEvent, merge } from 'rxjs';
import { sample, mapTo } from 'rxjs/operators';

const listener = merge(
  fromEvent(document, 'mousedown').pipe(mapTo(false)),
  fromEvent(document, 'mousemove').pipe(mapTo(true))
)
  .pipe(sample(fromEvent(document, 'mouseup')))
  .subscribe(isDragging => {
    console.log('Were you dragging?', isDragging);
  });

其他资源

• sample :newspaper: - 官方文档

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