数组的浅拷贝

改变其中一个另外一个也会变化

直接赋值，var newArr = this.oldArr

数组的深拷贝

改变其中一个数组另一个数组不会变化

1.for循环方式

var arr1 = [1, 2, 3];
var arr2 = [];
for (var i = 0; i < arr1.length; i++) {
    arr2.push(arr1[i]);
}
arr1[0] = 4;
console.log(arr1); //4, 2, 3
console.log(arr2); //1, 2, 3

2.concat方法，连接两个数组，不会改变原始数组，返回一个副本

var arr1 = [1, 2, 3];
var arr2 = arr1.concat();
arr1[0] = 4;
console.log(arr1); //4, 2, 3
console.log(arr2); //1, 2, 3

3.slice方法，截取数组，

var arr1 = [1, 2, 3];
var arr2 = arr1.slice(0);
arr1[0] = 4;
console.log(arr1); //4, 2, 3
console.log(arr2); //1, 2, 3

4.ES6扩展运算符实现数组的深拷贝

var arr1 = [1, 2, 3];
var [...arr2] = arr1;
arr1[0] = 4;
console.log(arr1); //4, 2, 3
console.log(arr2); //1, 2,