javascript - 对象原型(prototype)和继承

Question

// the original Animal class and sayName method
function Animal(name, numLegs) {
    this.name = name;
    this.numLegs = numLegs;
}
Animal.prototype.sayName = function() {
    console.log("Hi my name is " + this.name);
};

// define a Penguin class
function Penguin() {
    this.name = "penguin";
    this.numLegs = 2;
}

// set its prototype to be a new instance of Animal
var penguin = new Animal("Penguin", 2);

penguin.sayName();

编译器要求我“创建一个名为 penguin 的新 Penguin 实例”...

不确定我在这里做错了什么

Answer 1

以下是如何使用 JavaScript 中的原型(prototype)继承创建一个继承自 Animal 的 Penguin 对象:

// the original Animal class and sayName method
function Animal(name, numLegs) {
    this.name = name;
    this.numLegs = numLegs;
}
Animal.prototype.sayName = function() {
    console.log("Hi my name is " + this.name);
};


// define a Penguin class
function Penguin() {
    this.name = "penguin";
    this.numLegs = 2;
}
// set its prototype to be a new instance of Animal
Penguin.prototype = new Animal();


// Create new Penguin
var penguin = new Penguin();

penguin.sayName(); // outputs "Hi my name is penguin"
var legCount = penguin.numLegs; // outputs 2

这里有一篇文章详细解释了 JavaScript 原型(prototype)继承: http://pietschsoft.com/post/2008/09/JavaScript-Prototypal-Inheritence-Explained-in-Simple-Terms