filter

函数签名: filter(select: Function, thisArg: any): Observable

发出符合给定条件的值。

如果你希望当不满足条件时完成 observable 的话，请查阅 takeWhile！

示例

示例 1: 过滤出偶数

( StackBlitz | jsBin | jsFiddle )

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

// 发出 (1,2,3,4,5)
const source = from([1, 2, 3, 4, 5]);
// 过滤掉奇数
const example = source.pipe(filter(num => num % 2 === 0));
// 输出: "Even number: 2", "Even number: 4"
const subscribe = example.subscribe(val => console.log(`Even number: ${val}`));

示例 2: 基于属性过滤对象

( StackBlitz | jsBin | jsFiddle )

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

// 发出 ({name: 'Joe', age: 31}, {name: 'Bob', age:25})
const source = from([{ name: 'Joe', age: 31 }, { name: 'Bob', age: 25 }]);
// 过滤掉年龄小于30岁的人
const example = source.pipe(filter(person => person.age >= 30));
// 输出: "Over 30: Joe"
const subscribe = example.subscribe(val => console.log(`Over 30: ${val.name}`));

示例 3: 过滤出大于给定值的数字

( StackBlitz | jsBin | jsFiddle )

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

// 每1秒发出值
const source = interval(1000);
// 过滤掉所有值知道 interval 发出的值大于5
const example = source.pipe(filter(num => num > 5));
/*
  "Number greater than 5: 6"
  "Number greater than 5: 7"
  "Number greater than 5: 8"
  "Number greater than 5: 9"
*/
const subscribe = example.subscribe(val =>
  console.log(`Number greater than 5: ${val}`)
);

相关食谱

• HTTP 轮询
• 游戏循环

其他资源

• filter :newspaper: - 官方文档
• 使用 filter 添加条件逻辑 :video_camera: :dollar: - John Linquist
• 过滤操作符: filter :video_camera: :dollar: - André Staltz

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