js深度copy的几种实现

方法一：

function deepCopy(obj){
            var o;
            switch(typeof obj){
            case 'undefined': break;
            case 'string'   : o = obj + '';break;
            case 'number'   : o = obj - 0;break;
            case 'boolean'  : o = obj;break;
            case 'object'   :
                if(obj === null){
                    o = null;
                }else{
                    if(obj instanceof Array){
                        o = [];
                        for(var i = 0, len = obj.length; i < len; i++){
                            o.push(deepCopy(obj[i]));
                        }
                    }else{
                        o = {};
                        for(var k in obj){
                            o[k] = deepCopy(obj[k]);
                        }
                    }
                }
                break;
            default:
                o = obj;break;
            }
            return o;
        }

方法二：

function deepCopy(obj) {
        return JSON.parse(JSON.stringify(obj));
    }

方法三：

function deepCopy(obj){
            var newobj, obj;
            if (obj.constructor == Object){
                newobj = new obj.constructor();
            }else{
                newobj = new obj.constructor(obj.valueOf());//valueOf()方法返回 Array 对象的原始值
            }
            for(var key in obj){
                if ( newobj[key] != obj[key] ){
                    if ( typeof(obj[key]) == 'object' ){
                        newobj[key] = deepCopy(obj[key]);
                    }else{
                        newobj[key] = obj[key];
                    }
                }
            }
            newobj.toString = obj.toString;
            newobj.valueOf = obj.valueOf;
            return newobj;
        }

方法四：

var cloneObj = function(obj){
    var str, newobj = obj.constructor === Array ? [] : {};
    if(typeof obj !== 'object'){
        return;
    } else if(window.JSON){
        str = JSON.stringify(obj), //系列化对象
        newobj = JSON.parse(str); //还原
    } else {
        for(var i in obj){
            newobj[i] = typeof obj[i] === 'object' ? 
            cloneObj(obj[i]) : obj[i]; 
        }
    }
    return newobj;
};

方法五：

function deepCopy(p,c){
        c = c || {};
        for (var i in p){
            if(p.hasOwnProperty(i)){
                if(typeof p[i] === 'object'){
                    c[i] = Array.isArray(p[i]) ? [] : {};
                    deepCopy(p[i],c[i]);
                }else{
                    c[i] = p[i];
                }
            }
        }
        return c;
    }

另: object.assign()只有在obj属性层级为一的时候才为深拷贝

function deepCopy(obj) {
  return object.assign({}, obj);
}

方法六:

  function typeOf (obj) {
    const toString = Object.prototype.toString
    const 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'
    }
    return map[toString.call(obj)]
  }
  function deepCopy (obj) {
    const t = typeOf(obj)
    let o

    if (t === 'array') {
      o = []
    } else if (t === 'object') {
      o = {}
    } else {
      return obj
    }

    if (t === 'array') {
      for (let i = 0; i < obj.length; i++) {
        o.push(this.deepCopy(obj[i]))
      }
    } else if (t === 'object') {
      for (let i in obj) {
        o[i] = this.deepCopy(obj[i])
      }
    }
    return o
  },

方法七:

/*
提前安装lodash，在自己js里使用
*/
import _ from 'lodash'
let newVal = _.cloneDeep(datas)