一些程序员建议不要在 Javascript 中使用伪经典继承，但建议使用鸭子类型并为每个对象提供一组功能。

有没有一个很好的例子来说明如何做到这一点？我在下面有一个示例，但它一次只分配一个功能。我们可以给一个对象分配一整组方法吗，比如我们可以设置一个OceanAnimal的原型(prototype)吗？可以“游泳”、“潜水”和“上升”，LandAnimal 的原型(prototype)对于“run”、“walk”和“jump”，让一个对象从其中一个或两个继承？ (所以鱼对象可以继承或获得 OceanAnimal 的功能，而乌龟可以同时获得 OceanAnimal 和 LandAnimal 的功能？)

var yoyo = {
    name: "Yoyo",
    type: "turtle"
}

var simba = {
    name: "Simba",
    type: "lion"
}

var dolphy = {
    name: "Dolphy",
    type: "dolphin"
}

function swim(n) {
    console.log("My name is", this.name, ", I am a", this.type, "and I just swam", n, "feet")
}

function run(n) {
    console.log("My name is", this.name,  ", I am a", this.type, "and I just ran", n, "feet")
}

Object.prototype.respondTo = function(method) {
    return !!(this[method] && (typeof this[method] === "function"));
}

yoyo.swim = swim;
yoyo.swim(10);

dolphy.swim = swim;
dolphy.swim(80);

simba.run = run;
simba.run(200);

yoyo.run = run;
yoyo.run(2);

yoyo.walk = run;
yoyo.walk(1);

console.log(simba.respondTo("swim"));
console.log(simba.respondTo("run"));
console.log(simba.respondTo("walk"));

console.log(yoyo.respondTo("run"));
console.log(yoyo.respondTo("walk"));
console.log(yoyo.respondTo("fly"));

if(dolphy.respondTo("run")) {
    dolphy.run(10);
}

if(dolphy.respondTo("swim")) {
    dolphy.swim(10);
}

My name is Yoyo , I am a turtle and I just swam 10 feet 
My name is Dolphy , I am a dolphin and I just swam 80 feet 
My name is Simba , I am a lion and I just ran 200 feet 
My name is Yoyo , I am a turtle and I just ran 2 feet 
My name is Yoyo , I am a turtle and I just ran 1 feet 
false 
true 
false 
true 
true 
false 
My name is Dolphy , I am a dolphin and I just swam 10 feet

最佳答案

JavaScript 中的函数是通用的。它们可以用作 subroutines , methods , constructors , namespaces , modules ， 以及更多。

人们反对在 JavaScript 中使用伪经典继承的原因是因为它隐藏了 JavaScript 的真正威力。如果不比对象更具表现力，函数也同样具有表现力。 Alonzo Church 已经证明了这一点谁的工作，Lambda Calculus , 是 Turing Complete .

为了直接回答您的问题，我将使用函数来创建 Turtle , 一个 Lion和 Dolphin .然后我将演示乌龟是如何成为 OceanAnimal 的。和 LandAnimal , 狮子怎么只有LandAnimal ，以及海豚如何只是 OceanAnimal .最后，我将解释什么是鸭式打字。

首先让我们为 OceanAnimal 创建构造函数。 :

function OceanAnimal() {
    this.swim = function (n) {
        return "I am " + this.name + ", the " + this.type +
               ", and I just swam " + n + " meters.";
    };
}

function LandAnimal() {
    this.walk = function (n) {
        return "I am " + this.name + ", the " + this.type +
               ", and I just walked " + n + " meters.";
    };
}

Turtle.prototype.type = "turtle";

function Turtle(name) {
    this.name = name;
    LandAnimal.call(this);
    OceanAnimal.call(this);
}

Lion.prototype.type = "lion";

function Lion(name) {
    this.name = name;
    LandAnimal.call(this);
}

Dolphin.prototype.type = "dolphin";

function Dolphin(name) {
    this.name = name;
    OceanAnimal.call(this);
}

var yoyo = new Turtle("Yoyo");
var simba = new Lion("Simba");
var dolphy = new Dolphin("Dolphy");

alert(yoyo.walk(10));
alert(yoyo.swim(30));   // turtles are faster in the water
alert(simba.walk(20));
alert(dolphy.swim(20));

function isOceanAnimal(object) {
    if (typeof object !== "object") return false;
    if (typeof object.swim !== "function") return false;
    return true;
}

function isLandAnimal(object) {
    if (typeof object !== "object") return false;
    if (typeof object.walk !== "function") return false;
    return true;
}

When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck.

When I see an animal which swims like an ocean animal, I call that animal an ocean animal; and when I see an animal which walks like a land animal, I call that animal a land animal.

关于javascript - Javascript鸭子打字的例子？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12762550/