深拷贝和浅拷贝

浅拷贝：本质上是拷贝引用地址

let obj = {
    str:"string",
    fn:function(){
        console.log("hello world")
    },
    arr:[1,2,3,[4,5]]
}

let shallowCopy = function(obj){
    if(typeof obj != "object"||typeof obj == null){
        return obj
    }
    let copyTarget = new obj.constructor()
    for(let key in obj){
        if(obj.hasOwnProperty(key)){
            copyTarget[key] = obj[key]
        }
    }
    return copyTarget
}
console.log(shallowCopy(obj))
console.log(shallowCopy(obj).fn)

简化的深拷贝：将整个对象拷贝到另一个地址栏

let obj = { 
    str:"string", 
    fn:function(){ 
        console.log("hello world") 
    }, 
    arr:[1,2,3,[4,5]] 
}

let deepCopy = function(obj){
    if(typeof obj != 'object'||typeof obj == null){
        return obj
    }
    let copyTarget = new obj.constructor()
    for(let key in obj){
        if(obj.hasOwnProperty(key)){
            copyTarget[key] = deepCopy(obj[key])
        }
    }
    return copyTarget
}
console.log(shallowCopy(obj))
console.log(shallowCopy(obj).fn)

深拷贝-->处理循环引用情况-->也就是A引用B，B又引用A。这种情况下，如果是常规的递归会一直循环往复直到超出内存限制。-->map记录

let deepCopyPlus = function(obj,map = new Map()){
    if(typeof obj != 'object'||typeof obj == null){
        return obj
    }
    let copyTarget = new obj.constructor()
    //添加一个map作为记录
    if(map.has(obj)){
        return map.get(obj)
    }
    map.set(obj,copyTarget)
    for(let key in obj){
        if(obj.hasOwnProperty(key)){
            copyTarget[key] = deepCopyPlus(obj[key],map)
        }
    }
    return copyTarget
}