ES6中js新增rest参数，用来获取函数的实参

function fn(...args){
  console.log(...args)   //输出[1,2,3]

fn(1,2,3)

rest参数要放在最后，输出都是数组

function fn(a，b，...args){
  console.log(a) //输出 1 
  console.log(b) //输出2 
  console.log(...args)   //输出[3]

fn(1,2,3)