util核心模块(require(“utils"))提供了一个创建函数原型链。该函数称为 inherits ，并采用一个子类继之以父类。
var inherits = require("util").inherits;
/*www.w3cschool.cn*/function Car(n){
this.name = n;
}
Car.prototype.drive= function (destination) {
console.log(this.name, "can drive to", destination);
}
function FlyingCar(name) {
// Call parent constructor
Car.call(this, name); // Additional construction code
}
inherits(FlyingCar, Car);
// Additional member functions
FlyingCar.prototype.fly = function (destination) {
console.log(this.name, "can fly to", destination);
}
var bird = new FlyingCar("XXX");
bird.drive("New York");
bird.fly("Seattle");上面的代码生成以下结果。
覆盖子类中的函数
要覆盖父函数但仍使用一些原始功能，只需执行以下操作:
在子原型上创建一个具有相同名称的函数。调用父函数类似于我们调用父构造函数的方法，基本上使用
Parent.prototype.memberfunction.call(this, /*any original args*/) syntax.
// www.w3cschool.cn// util function
var inherits = require("util").inherits;
// Base
function Base() {
this.message = "message";
};
Base.prototype.foo = function () {
return this.message + " base foo" };
// Child
function Child() { Base.call(this); };
inherits(Child, Base);
// Overide parent behaviour in child
Child.prototype.foo = function () {
// Call base implementation + customize
return Base.prototype.foo.call(this) + " child foo";
}
// Test:
var child = new Child();
console.log(child.foo()); // message base foo child foo上面的代码生成以下结果。
检查继承链
var inherits = require("util").inherits;
/*from www.ancii.com*/function A() { }
function B() { }; inherits(B, A);
function C() { }
var b = new B();
console.log(b instanceof B); // true because b.__proto__ == B.prototype
console.log(b instanceof A); // true because b.__proto__.__proto__ == A.prototype
console.log(b instanceof C); // false