OOP Javascript与Java(或其他,如PHP)

Question

我有点理解JOP和Java在OOP方面的区别.我阅读了Javascript书中的底部段落,但我不完全理解它的含义,你能进一步解释并提供示例来展示两种语言之间的区别吗？

"在许多面向对象的编程语言中,可以定义一类对象,然后创建作为该类实例的单个对象."

谢谢!

Answer 1

什么大多数人做的是使用构造函数,像这样:

function MyClass(a, b) {
    // Private instance properties
    var x = "secret";
    var y = "also secret";

    // Public instance properties
    this.a = a;
    this.b = b;

    // "Privileged" methods; can access private and public properties
    this.foo = function () {
        return x + " " + this.a;
    };
}

// "Public" methods; cannot access private properties
MyClass.prototype.bar = function () {
    return this.a + " " + this.b;
};

// Public shared properties; not recommended:
MyClass.prototype.w = "stuff";

// Static methods
MyClass.baz = function () {
    return "i am useless";
};

然后,您将使用此构造函数,如下所示:

var instance = new MyClass("hi", "Meen");

asssert.equal(instance.foo(), "secret hi");
assert.equal(instance.bar(), "hi Meen");
assert.equal(MyClass.baz(), "i am useless");

var also = new MyClass("hi", "Raynos");

instance.w = "more stuff";
assert.equal(also.w, "more stuff");

如果你想继承,你会做类似的事情:

function Inherited(a) {
    // apply parent constructor function
    MyClass.call(this, a, "Domenic");
}
Inherited.prototype = Object.create(MyClass.prototype);

var inherited = new Inherited("hello there good chap");

assert.equal(inherited.a, "hello there good chap");
assert.equal(inherited.foo(), "secret hello there good chap");
assert.equal(inherited.bar(), "hello there good chap Domenic");