javascript封装 - 任何访问私有成员给定实例的方法？ [英] javascript encapsulation - any way to access a private member given instance?

问题描述

在给定实例变量的情况下，是否可以在javascript中访问私有成员？例如，

Is it possible to access a private member in javascript given an instance variable? For example,

function class Foo() {
   var x=12;
   // some other stuff
}
F = new Foo();
// how to get/set F.x?

更新：假设该类具有特权方法。是否有可能劫持这种特权方法来访问私有成员？

Update: as a twist, suppose that the class has a privileged method. Is it possible to hijack that privileged method to access a private member?

function class Foo() {
   var x=12, y=0;
   this.bar = function(){ y=y+1; }
}
F = new Foo();
// can I modify Foo.bar to access F.x?

推荐答案

你需要一个特权方法获取/设置 x 的值：

You'll need a privileged method to get/set the value of x:

function Foo() {
    var x = 12;
    this.getX = function() { return x; };
    this.setX = function(v) { x = v; };
}

var f = new Foo(),
    g = new Foo();

f.getX(); // returns 12
g.getX(); // returns 12

f.setX(24);

f.getX(); // returns 12
g.getX(); // returns 24

g.setX(24); 

f.getX(); // returns 24
g.getX(); // returns 24

现场演示： http://jsfiddle.net/simevidas/j7VtF/

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