es6 扩展运算符 “...”

//展开数组
let a = [1,2,3,4,5],
b = [...a,6,7];
console.log(b);
//打印出来的值[1, 2, 3, 4, 5, 6, 7]

//数组的拷贝
var c = [1, 2, 3];
var d = [...c]; 
d.push(4); 
console.log(d);

//打印出来的值[1, 2, 3, 4]

//数组的合并
var j = [7, 1, 2];
var k = [5, 0, 8];
j = [...k, ...j];
console.log(j)

//打印出来的值[5, 0, 8, 7, 1, 2]

//展开函数调用
function  fn(a,b,c,d){
  console.log(a+b+c+d);
}
var p=[1,9,3,,6];
let result=fn(5,...p);开函数的调用
//打印出来的值18