js常用方法模拟

深拷贝

function cloneDeep(obj,hash = new WeakMap()){
    if(obj==null || typeof obj !== 'object') return obj;
    if(obj instanceof Date) return new Date(obj);
    if(obj instanceof RegExp) return new RegExp(obj);
    if(hash.get(obj)) return hash.get(obj);
    
    var cloneObj = new obj.constructor;
    hash.set(obj,cloneObj);
    for(var key in obj){
        if(obj.hasOwnProperty(key)){
            cloneObj[key] = cloneDeep(obj[key],hash);
        }
    }
    return cloneObj;
}

var obj = {name:'wyy',outer:{inner:'test'}};
obj.o = obj;
var clone = cloneDeep(obj);
console.log(obj,clone);

模拟new

function create(){
    // 1、获得构造函数，同时删除 arguments 中第一个参数
    var Con = [].shift.call(arguments);
    // 2、创建一个空的对象并链接到原型，obj 可以访问构造函数原型中的属性
    obj = Object.create(Con.prototype);
    // 3、绑定 this 实现继承，obj 可以访问到构造函数中的属性
    var ret = Con.apply(obj,arguments);
    // 4、优先返回构造函数返回的对象
    return ret instanceof Object?ret:obj;
}

function Car(color){
    this.color = color;
    return {a:12}
}
var obj = create(Car,'red')

模拟bind

Function.prototype.mybind = function(context){
    if (typeof this !== "function") {
      throw new Error("Function.prototype.bind - what is trying to be bound is not callable");
    }
    var self = this;
    var args = [].slice.call(arguments,1);
    var fBind = function(){
        var innerArgs = [].slice.call(arguments);
        self.apply(this instanceof fBind?this:context,args.concat(innerArgs));
    }
    fBind.prototype = Object.create(this.prototype);
    return fBind;
}

var obj = {
    name:'wyy'
}
function bar(color){
    this.color = color;
    console.log(this.color,color);
}
var barFn = bar.mybind(obj,'red');
new barFn();