SOURCE

function deepClone(obj) {
    //先判断是否是一个对象
    if(typeof obj !=="object") return

    let newArr = obj instanceof Array ? [] :{}

    //循环对象属性
    for(let key in obj){
        //自身属性
        if(obj.hasOwnProperty(key)){
            //对象属性不存在新对象中
            if(!(key in newArr)){
                //日期类型
                if(obj[key] instanceof Date){
                    newArr[key] = new Date(obj[key].getTime())
                }
                //正则类型
                else if(obj[key] instanceof RegExp){
                    newArr [key] = new RegExp(obj[key])
                }
                //dom树类型 obj[key].nodeType ===1
                else if(typeof obj[key] === 'object' && obj[key] instanceof HTMLDocument){
                    let elm = document.getElementsByTagName(key)[0]
                    newArr[key] = elm.cloneNode(elm)
                }else{
                    newArr[key] = typeof obj[key] === 'object' ? deepClone(obj[key]):obj[key]
                }
            }
        }
    }
    return newArr
}

// deepClone 函数测试效果
const objA = {
  name: 'jack',
  birthday: new Date(),
  pattern: /jack/g,
  body: document.body,
  others: [123,'coding', new Date(), /abc/gim,]
};

const objB = deepClone(objA);
console.log(objA === objB); // 打印 false
console.log(objA, objB);