扩展运算符... 的使用

// 1、合并数组
let arr1 = [1,2,3];
let arr2 = [4,5]
let arr3 = [...arr1,...arr2];

console.log(arr3); //[1, 2, 3, 4, 5]
console.log([...arr1,...arr2]);//[1, 2, 3, 4, 5]


let arrA = [1,2,3];
let arrB = [4,5,...arrA];
let arrC = [...arrA,4,5];

console.log(arrB,arrC); // [4, 5, 1, 2, 3]   [1, 2, 3, 4, 5]

// 2、合并对象
let obj = { a:1,b:2 };
let obj2 = { ...obj };
console.log(obj2)
//{ a: 1, b: 2 }
console.log(obj == obj2)

//3、函数传值
function fn(a,b,c){
    console.log(a)
    console.log(b)
    console.log(c)
}


let arr = [1,2,3];
//ES6
fn(...arr);

// 4、配合解构使用
let [a,...arr11] = [1,2,3,4,5];
console.log(a); //1
console.log(arr11) //[ 2, 3, 4, 5 ]

let {a,...obj} = {a:1, b:"1", c:function(){}, d:null, e:undefined, e:Symbol};
console.log(a);
//1
console.log(obj);
//{ b: '1', c: [Function: c], d: null, e: [Function: Symbol] }