3点运算符

• 用途

1. rest(可变)参数
   • 用来取代arguments 但比 arguments 灵活,只能是最后部分形参参数
     function fun(...values) {
     console.log(arguments);
     arguments.forEach(function (item, index) {
     console.log(item, index);
     });
     console.log(values);
     values.forEach(function (item, index) {
     console.log(item, index);
     })
     }
     fun(1,2,3);
2. 扩展运算符
   let arr1 = [1,3,5];
   let arr2 = [2,...arr1,6];
   arr2.push(...arr1);

function foo(a, ...value){
        console.log(arguments);
        // arguments.callee();
        console.log(value);
        /*arguments.forEach(function(item, index){
            console.log(item, index);
        })*/
        value.forEach(function(item, index){
            console.log(item, index);
        })
    }
    foo(2, 65, 33, 44);
    let arr = [1,6];
    let arr1 = [2,3,4,5];
    arr = [1, ...arr1, 6];
    console.log(arr);
    console.log(...arr);