Question

map

函数签名: map(project: Function, thisArg: any): Observable

对源 observable 的每个值应用投射函数。

示例

示例 1: 每个数字加10

( StackBlitz | jsBin | jsFiddle )

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

// 发出 (1,2,3,4,5)
const source = from([1, 2, 3, 4, 5]);
// 每个数字加10
const example = source.pipe(map(val => val + 10));
// 输出: 11,12,13,14,15
const subscribe = example.subscribe(val => console.log(val));

示例 2: 映射成单一属性

( StackBlitz | jsBin | jsFiddle )

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

// 发出 ({name: 'Joe', age: 30}, {name: 'Frank', age: 20},{name: 'Ryan', age: 50})
const source = from([
  { name: 'Joe', age: 30 },
  { name: 'Frank', age: 20 },
  { name: 'Ryan', age: 50 }
]);
// 提取每个 person 的 name 属性
const example = source.pipe(map(({ name }) => name));
// 输出: "Joe","Frank","Ryan"
const subscribe = example.subscribe(val => console.log(val));

相关食谱

• 智能计数器
• 游戏循环
• HTTP 轮询

其他资源

• map :newspaper: - 官方文档
• map vs flatMap :video_camera: - Ben Lesh
• 转换操作符: map 和 mapTo :video_camera: :dollar: - André Staltz

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