jsnew、object.create、bind的模拟实现【转载备忘】

//创建Person构造函数&＃xff0c;参数为name,age
function Person(name,age){this.name &＃61; name;this.age &＃61; age;
}function _new(){//1.拿到传入的参数中的第一个参数&＃xff0c;即构造函数名Funcvar Func &＃61; [].shift.call(arguments);//2.创建一个空对象obj,并让其继承Func.prototypevar obj &＃61; Object.create(Func.prototype);//3.执行构造函数&＃xff0c;并将this指向创建的空对象obj
Func.apply(obj,arguments)//4.返回创建的对象objreturn obj
}xm &＃61; _new(Person,&＃39;xiaoming&＃39;,18);console.log(xm);

if (typeof Object.create !&＃61;&＃61; "function") {Object.create &＃61; function (proto, propertiesObject) {if (typeof proto !&＃61;&＃61; &＃39;object&＃39; && typeof proto !&＃61;&＃61; &＃39;function&＃39;) {throw new TypeError(&＃39;Object prototype may only be an Object: &＃39; &＃43; proto);} else if (proto &＃61;&＃61;&＃61; null) {throw new Error("This browser&＃39;s implementation of Object.create is a shim and doesn&＃39;t support &＃39;null&＃39; as the first argument.");}if (typeof propertiesObject !&＃61; &＃39;undefined&＃39;) throw new Error("This browser&＃39;s implementation of Object.create is a shim and doesn&＃39;t support a second argument.");function F() {}F.prototype &＃61; proto;return new F();};
}

if (!Function.prototype.bind) {Function.prototype.bind &＃61; function(oThis) {if (typeof this !&＃61;&＃61; &＃39;function&＃39;) {// closest thing possible to the ECMAScript 5// internal IsCallable functionthrow new TypeError(&＃39;Function.prototype.bind - what is trying to be bound is not callable&＃39;);}var aArgs &＃61; Array.prototype.slice.call(arguments, 1),fToBind &＃61; this,fNOP &＃61; function() {},fBound &＃61; function() {// this instanceof fNOP &＃61;&＃61;&＃61; true时,说明返回的fBound被当做new的构造函数调用return fToBind.apply(this instanceof fNOP? this: oThis,// 获取调用时(fBound)的传参.bind 返回的函数入参往往是这么传递的
aArgs.concat(Array.prototype.slice.call(arguments)));};// 维护原型关系if (this.prototype) {// Function.prototype doesn&＃39;t have a prototype propertyfNOP.prototype &＃61; this.prototype; }// 下行的代码使fBound.prototype是fNOP的实例,因此// 返回的fBound若作为new的构造函数,new生成的新对象作为this传入fBound,新对象的__proto__就是fNOP的实例fBound.prototype &＃61; new fNOP();return fBound;};
}