js中如何复制一个数组(浅复制、深复制)

  var arr = [1, 2, 3];
  var newArr = arr;
  arr.push(4);
  console.log(newArr1);  // [1, 2, 3, 4]

  var arr = [1, 2, 3];
  var newArr = arr.concat();
  arr.push(4);
  console.log(newArr); // [1, 2, 3]

  var arr = [1, 2, 3];
  var newArr = arr.slice();
  arr[0] = 10;
  console.log(arr);// [10, 2, 3]
  console.log(newArr);// [1, 2, 3]

  var arr = [1, 2, 3];
  var [ ...newArr ] = arr;
  arr[0] = 10;
  console.log(arr); // [10, 2, 3]
  console.log(newArr);// [1, 2, 3]

 var arr = [1, 2, 3];
 var newArr = Object.assign([], arr);
 arr[0] = 10;
 console.log(arr);// [10, 2, 3]
 console.log(newArr);// [1, 2, 3]

  var arr = [ { a: 1 }, [ 1, 2 ], 3 ];
  let newArr = arr.concat();
  arr[0].a = 2;
  console.log(arr); // [ { a: 2 }, [ 1, 2 ], 3 ]
  console.log(newArr);// [ { a: 2 }, [ 1, 2 ], 3 ] 值被影响

  var arr = [ { a: 1 }, [ 1, 2 ], 3 ];
  // let newArr = JSON.parse(JSON.stringify(arr));
  let newArr = arr.concat();
  arr[0].a = 2;
  console.log(arr); // [ { a: 2 }, [ 1, 2 ], 3 ]
  console.log(newArr);// [ { a: 1 }, [ 1, 2 ], 3 ]

let a = {
  age: undefined,
  sex: Symbol('male'),
  jobs: function() {},
  name: 'sun'
}
let b = JSON.parse(JSON.stringify(a))
console.log(b) // {name: "sun"}

  var deepCopy = function(obj) {
    // 判断是否是对象
    if (typeof obj !== 'object') return;
    // 判断obj类型，根据类型新建一个对象或者数组
    var newObj = obj instanceof Array ? [] : {}
    // 遍历对象，进行赋值
    for (var key in obj) {
      if (obj.hasOwnProperty(key)) {
        let val = obj[key];
        // 判断属性值的类型，如果是对象，递归调用deepCopy
        newObj[key] = typeof val === 'object' ? deepCopy(val) : val
      }
    }
    return newObj
  }

_.cloneDeep(value)

var objects = [{ 'a': 1 }, { 'b': 2 }];
var deep = _.cloneDeep(objects);
console.log(deep[0] === objects[0]);
// => false

npm i --save lodash

import _ from 'lodash';
Vue.prototype._ = _;

let newObj = this._.cloneDeep(oldObj)