数组的浅拷贝与深拷贝
浅拷贝只复制第一层，深拷贝全部复制
浅拷贝：
// es6
const arr1 = [1, 2, 3, [4, 5, 6]];
const [...arr2] = arr1;
// es5
var arr1 = [1, 2, 3, [4, 5, 6]];
var arr2 = arr1.slice();
arr2.push(7);
arr2[3].push(7);
arr1 // [1, 2, 3, [4, 5, 6, 7]];
arr2 // [1, 2, 3, [4, 5, 6, 7], 7];
深拷贝（需使用递归）：
const arrayDeep = (targetArray) => {
const array = [];
targetArray.map(item => {
if(Object.prototype.toString.call(item) === '[object Object]') {
const obj = {};
for(let i in item) {
obj[i] = item[i];
// 对象属性为数组
if(Object.prototype.toString.call(item[i]) === '[object Array]') {
obj[i] = arrayDeep(item[i]);
}
}
array.push(obj);
}else if(Object.prototype.toString.call(item) === '[object Array]') {
//多维数组，递归
array.push(arrayDeep(item));
}else {
array.push(item);
}
});
return array;
}
const arrays = [{a: 2}, {b: 5, child:[{c: 3}, {d: 4}]}, {f:7}, "333", 5, ['wqfe', {e:7}]];
const arr = arrayDeep(arrays);
arr[5][1].e = 5;
console.log(arr[5][1].e); //5
console.log(arrays[5][1].e); //7