引用类型的数据'='号赋值和循环赋值的区别

直接等号赋值相当于添加了一个指针指向该内存
当你修改赋值后的数据，原来的数据也会发生改变（），如下

let obj = {name:"1",age:"10"}
let obj2 = obj
obj2.name = '2'
console.log(obj)
打印结果： {name: '2', age: '10'}

当你循环赋值的时候，开辟一个新的堆内存，两个内存不会有关联（深拷贝）

let obj = {name:"1",age:"10"}
let obj2 = {}
for(let key in obj){
  obj2[key] = obj[key]
}
obj2.age = 1000
console.log(obj)
console.log(obj2)
VM1358:7 {name: '1', age: '10'}
VM1358:8 {name: '1', age: 1000}

最后贴一段深拷贝的代码

/**
 * 对象深拷贝
 */
export const deepClone = (data) => {
  var type = getObjType(data);
  var obj;
  if (type === "array") {
    obj = [];
  } else if (type === "object") {
    obj = {};
  } else {
    // 不再具有下一层次
    return data;
  }
  if (type === "array") {
    for (var i = 0, len = data.length; i < len; i++) {
      obj.push(deepClone(data[i]));
    }
  } else if (type === "object") {
    for (var key in data) {
      obj[key] = deepClone(data[key]);
    }
  }
  return obj;
};

获取对象类型getObjType

export const getObjType = (obj) => {
  var toString = Object.prototype.toString;
  var map = {
    "[object Boolean]": "boolean",
    "[object Number]": "number",
    "[object String]": "string",
    "[object Function]": "function",
    "[object Array]": "array",
    "[object Date]": "date",
    "[object RegExp]": "regExp",
    "[object Undefined]": "undefined",
    "[object Null]": "null",
    "[object Object]": "object",
  };
  if (obj instanceof Element) {
    return "element";
  }
  return map[toString.call(obj)];
};