是否可以动态访问模块模式中的私有变量？

Question

Is there a way to have a public function from the module-pattern accessing private variables dynamically? test1 shows what I mean with "access dynamically" but with public variables

var x = (function(){
    var x=0, y=2, z=5;

    return {
        toast: 123,
        test1: function(arg){
            return this[arg];
        },
        test2: function(){
            // ??
        }
    };
}());

console.log(x.test1("toast")); // 123
console.log(x.test2("y")); // should return 2

I ended up with creating a single private variable (an object) storing my private variables so I was able to access them like that

 privateVarStore[privateVarName]

But is there another solution for that?

Answer 1

DEMO

Yes.

Sorry to disappoint Adam Rackis but you can do it with (the evil ) eval:

var x = (function(){
    var x=0, y=2, z=5;

    return {
        toast: 123,
        test1: function(arg){
            return this[arg];
        },
        test2: function(a){
            return eval(a)
        }
    };
}());

console.log(x.test1("toast")); // 123
console.log(x.test2("y")); // should return 2  -> does return 2

This is one of those few exceptions where eval should be used.

EDIT, as per Hans B PUFAL suggestion (comment), you can and should validate the parameter in test2 as follows:

test2: function(a){
    return /^[$_a-z][$_a-z0-9]*$/i.test (a) ? eval(a) : undefined;
}

Answer 2

No (at least not without resorting to eval , per qwertymk's answer).

y is not a property of x (consider naming this object something better than x to avoid confusion with the local variable x ). y is a local variable over which x 's methods have formed a closure.

Any of x 's methods may access y , but not by saying this.y , but rather by accessing y directly.

Again, y is not a property of your object x . It's just a local variable in the function that created x , thereby causing x 's methods to form a closure over it.

So, to get test2 to return y , just do:

test2: function(){
    return y;
}

---

To create a method allowing you to access private variables, consider something like this:

var x = (function () {
    var privateMembers = { x: 0, y: 2, z: 5 };

    return {
        getPrivate: function (name) {
            return privateMembers[name];
        },
        toast: 123,
        test1: function (arg) {
             return this[arg];
        },
        test2: function () {
           // ??
        }
    };
})();

And then

alert(x.getPrivate("y")); //alerts 2

Check out this fiddle