浅谈nodejs中的类定义和继承的套路

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

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

 //开始成员变量定义
 this.className = "Base";
}

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

var base = Base(); //不使用new操作符，直接进行函数调用，自动调用new操作符
console.log(base.className);
base.printClassName();

var inherits = function(ctor, superCtor) {
 //严格相等测试:undefined/null
 //子类构造函数必须存在
 if (ctor === undefined || ctor === null)
 throw new TypeError('The constructor to "inherits" must not be ' +
 'null or undefined');
 //严格相等测试:undefined/null
 //父类构造函数必须存在
 if (superCtor === undefined || superCtor === null)
 throw new TypeError('The super constructor to "inherits" must not ' +
 'be null or undefined');

 //要点: 如果要继承的话，父类必须要有prototype对象
 //这也是为什么将所有成员方法都定义在prototype对象中！！！
 if (superCtor.prototype === undefined)
 throw new TypeError('The super constructor to "inherits" must ' +
 'have a prototype');

 //让子类构造函数对象增加一个super_指针，指向父类，这样就形成继承链
 ctor.super_ = superCtor;

 //调用Object.setPrototypeOf(子类的prototype,父类的prototype)
 Object.setPrototypeOf(ctor.prototype, superCtor.prototype);
};

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

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

//注意，inherits调用不在构造函数，也不在原型对象，而是全局调用
inherits(Child, Base);

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

 //增加这句话，在调用printClassName就能正常的