Question

groupBy

函数签名: groupBy(keySelector: Function, elementSelector: Function): Observable

基于提供的值分组成多个 observables

示例

示例 1: 根据属性分组

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { from } from 'rxjs';
import { groupBy, mergeMap, toArray } from 'rxjs/operators';

const people = [
  { name: 'Sue', age: 25 },
  { name: 'Joe', age: 30 },
  { name: 'Frank', age: 25 },
  { name: 'Sarah', age: 35 }
];
// 发出每个 people
const source = from(people);
// 根据 age 分组
const example = source.pipe(
  groupBy(person => person.age),
  // 为每个分组返回一个数组
  mergeMap(group => group.pipe(toArray()))
);
/*
  输出:
  [{age: 25, name: "Sue"},{age: 25, name: "Frank"}]
  [{age: 30, name: "Joe"}]
  [{age: 35, name: "Sarah"}]
*/
const subscribe = example.subscribe(val => console.log(val));

其他资源

• groupBy :newspaper: - 官方文档
• 使用 RxJS 的 groupBy 操作符分组成高阶 observables :video_camera: :dollar: - André Staltz
• 在真实的 RxJS 应用中使用 groupBy :video_camera: :dollar: - André Staltz

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