map 映射
函数定义
map<U>(callbackfn: (value: T, index: number, array: T[]) => U, thisArg?: any): U[];
一个简单的map映射示例
'use strict' var list = [1, 2, 3, 4, 5]; var newList = list.map(value => value * 2); console.log(newList); // [ 2, 4, 6, 8, 10 ]
使用map映射对象数据，给每个元素添加新的属性
'use strict' var list = [ { name: "Tom", age: 10 }, { name: "Jack", age: 20 } ]; var newList = list.map((item, index)=>{ return { index: index, name: item.name, age: item.age + 1, active: false } }); console.log(newList); /** [ { index: 0, name: 'Tom', age: 11, active: false }, { index: 1, name: 'Jack', age: 21, active: false } ] */
forEach 迭代
函数定义
forEach(callbackfn: (value: T, index: number, array: T[]) => void, thisArg?: any): void;
使用 forEach 给列表添加属性
'use strict' var list = [ { name: "Tom", age: 10 }, { name: "Jack", age: 20 } ]; list.forEach((item, index)=>{ item.age = item.age + 1; item.active = false; item.index = index; }); console.log(list); /** [ { name: 'Tom', age: 11, active: false, index: 0 }, { name: 'Jack', age: 21, active: false, index: 1 } ] */
区别
map 和 forEach 都是迭代列表元素，参数都相同
map有返回值，forEach无返回值
