javascript - 这个模块片段有什么问题？

Question

我想在对象中拥有私有(private)属性。以下代码不起作用:

var GameModule = (function(ns){

    function Game(ctx) {
        var self   = this, //use self in callback methods (requestAnimationFrame etc)
            ctx    = ctx,

        var dx = 1,
            dy = 1;

        console.log(dx, dy); //writes 1,1,

        console.log(self.dx, self.dy); //writes undefined, undefined
    }

    ns.Game = Game;
    return ns;

})(GameModule || {});

//somewhere later in a different file
$(document).ready(function(){
   var game = new GameModule.Game(some_ctx);
});

看起来 vars 类似于静态成员，而不是私有(private)成员。

我是否必须编写 this.dx = 1 以使变量可访问(例如在成员函数中)？它不会使变量公开吗？

Answer 1

要在 Javascript 中定义类属性，您可以这样做(Fiddle):

var Class = function(){

    this.property = 'now this is a property';

    Class.staticProperty = 'and this is a static property';

    var property = 'this is NOT a property, but a local variable';
};

Class.prototype.propertyToo = 'this is also a property';

var object = new Class();

console.log(object.property);
console.log(object.propertyToo);
console.log(Class.staticProperty);

JavaScript 语言本身没有提供任何访问修饰符，所以没有tricky methods 就不能实现私有(private)属性。 .