对象的函数解构

直接把这个JSON格式数据当作参数，传递到函数内部进行处理

let json = {            a:'jie',            b:'杰'        }        function fun({a,b}){            console.log(a,b);        }        fun(json) //jie 杰

数组的函数解构

let arr =['jie','biao','nine'];        function fun(a,b,c){            console.log(a,b,c)        }        fun(...arr)  //jie biao nine

in

in是用来判断对象或者数组中是否存在某个值的

对象

let obj={            a:'jie'        }        console.log('a' in obj) // true        console.log('b' in obj) //false

数组

这里的0指的是数组下标位置是否为空。

let arr = [,,,];        console.log(0 in arr);  //false        let arr2 = ['jie','bioa'];        console.log(0 in arr2) //true        console.log('jie' in arr2) //false

map

var arr2 = ['jie', 'bioa', 'nine'];        console.log(arr2.map(item => {            return item = "web"        })) (3) ["web", "web", "web"]         console.log(arr2.map(val => "web")) //(3) ["web", "web", "web"]

数组转为字符串

join

var arr2 = ['jie', 'bioa', 'nine'];        console.log(arr2.join('|'))   //jie|bioa|nine

toString

var arr2 = ['jie', 'bioa', 'nine'];        console.log(arr2.toString()) //jie,bioa,nine