ES6-- rest参数

toString.call(function(){})
// "[object Function]"
 
toString.call(null)
//"[object Null]"
 
toString.call([2])
"[object Array]"
 
toString.call(undefined)
//"[object Undefined]"
 
toString.call('stjd')
//"[object String]"
 
toString.call(1)
//"[object Number]"
 
toString.call(true)
//"[object Boolean]"
 
toString.call(Symbol(3))
// "[object Symbol]"
 
toString.call({q:8})
//"[object Object]"

原文链接：https://blog.csdn.net/qq_41831345/article/details/94428030

（...x）Rest 参数接受函数的多余参数，组成一个数组

function sum(x, y, m) {
                let total = 0;
                if (x) total += x;
                if (y) total += y;
                if (m) total += m;
                console.log(`total:${total}`)  //11
            }
            sum(5, 6)
            let sum1 = (...x)=>{  //
                let total=0;
                for(var i of x)
                {
                     total+=i;
                }
                console.log(`total:${total}`)
            }
           sum1(7,8,9)  //24


...[4,5]  //这就是扩展运算符 console.log(...[4,5])  //4 5
http://www.fly63.com/article/detial/2516

promise的用法
let checklogin = function() {
                return new Promise((resolve, reject) => {
                    var flag = document.cookie.indexOf("user") != -1 ? true : false;
                    if (true) {
                        resolve({
                            status: "success",
                        })
                    }
                })

            }
            let getUserInfor = ()=>{
                return new Promise((resolve,reject)=>{
                   resolve({
                        name:"李四",
                        age:18
                    })
                })
            }
            checklogin().then(res => {
                if(res.status == "success")
                {
                    return getUserInfor();
                }
            }).catch(err => {
                console.log('失败')
            }).then(res1=>{
                console.log(`userInfor:${res1.name}`)
            })
            
        Promise.all([checklogin(),getUserInfor()]).then(([res1,res2])=>{
            console.log(`res1:${res1.status}`)
        })