浅拷贝和深拷贝

对象浅拷贝

1、 Object.assign()

var obj = {
      name: 'zhang',
      info: {
        age: 10,
      },
      grade: [10, 20]
    }
var copyObj = Object.assign({}, obj)

2、es6 展开运算符...

var obj = {
      name: 'zhang',
      info: {
        age: 10,
      },
      grade: [10, 20]
    }
var copyObj =  { ... obj }

数组浅拷贝

1、Array.slice() 数组截取，返回新的数组

var arr = [10, {age: 1, info: {name: 'zhangsan'}}]
var copyArr = arr.slice()

2、Array.concat() 数组合并

var arr = [10, {age: 1, info: {name: 'zhangsan'}}]
var copyArr = arr.concat([], arr)

3、es6 展开运算符...

var arr = [10, {age: 1, info: {name: 'zhangsan'}}]
var copyArr = [...arr]

递归实现对象深拷贝

拷贝的时候判断一下属性值的类型，如果是对象，我们递归调用深拷贝函数
var obj = {
  name: 'zhang',
  info: {
    age: 10,
  },
  grade: [10, 20]
}

var deepCopy = function(obj) {
    if (typeof obj !== 'object') return;
    var newObj = obj instanceof Array ? [] : {};
    for (var key in obj) {
        if (obj.hasOwnProperty(key)) {
            newObj[key] = typeof obj[key] === 'object' ? deepCopy(obj[key]) : obj[key];
        }
    }
    return newObj;
}