function Base() {
 if (!(this instanceof Base)) {
 return new Base();
 }
}

function Base() {
 if (!(this instanceof Base)) {
 return new Base();
 }

 //開始成員變量定義
 this.className = "Base";
}

Base.prototype.printClassName = function(){
 console.log(this.className);
}

var base = Base(); //不使用new操作符，直接進行函數調用，自動調用new操作符
console.log(base.className);
base.printClassName();

var inherits = function(ctor, superCtor) {
 //嚴格相等測試:undefined/null
 //子類構造函數必須存在
 if (ctor === undefined || ctor === null)
 throw new TypeError('The constructor to "inherits" must not be ' +
 'null or undefined');
 //嚴格相等測試:undefined/null
 //父類構造函數必須存在
 if (superCtor === undefined || superCtor === null)
 throw new TypeError('The super constructor to "inherits" must not ' +
 'be null or undefined');

 //要點: 如果要繼承的話，父類必須要有prototype對象
 //這也是為什么將所有成員方法都定義在prototype對象中！！！
 if (superCtor.prototype === undefined)
 throw new TypeError('The super constructor to "inherits" must ' +
 'have a prototype');

 //讓子類構造函數對象增加一個super_指針，指向父類，這樣就形成繼承鏈
 ctor.super_ = superCtor;

 //調用Object.setPrototypeOf(子類的prototype,父類的prototype)
 Object.setPrototypeOf(ctor.prototype, superCtor.prototype);
};

// 僅適用于Chrome和FireFox，在IE中不工作：
Object.setPrototypeOf = Object.setPrototypeOf || function (obj, proto) {
 obj.__proto__ = proto;
 return obj; 
}

function Child() {
 //老樣子，套路1
 if (!(this instanceof Child)) {
 return new Child();
 }
}

//注意，inherits調用不在構造函數，也不在原型對象，而是全局調用
inherits(Child, Base);

function Child() {
 //老樣子，套路1
 if (!(this instanceof Child)) {
 return new Child();
 }

 //增加這句話，在調用printClassName就能正常的