reduce的使用

[DongLee0504]

提取对象的某些属性

let res = {
        name: 'lidong',
        age: 18,
        sports: 'baseketball'
    },
    obj,
    arr = ['name'];
    obj = arr.reduce((p, n) => {
        if(n in res) {
            p[n] = res[n]
        };
        return p
    },{})
    console.log(obj); // {name: "lidong"}

计算出一个字符串中每个字符出现的次数

let str = 'hello world';
    let obj2 = str.split('').reduce((acc, item) => {
        acc[item] = (acc[item] || 0) + 1;
        return acc
    }, {});
    console.log(obj2) // {h: 1, e: 1, l: 3, o: 2, " ": 1, …}