Question

Is it possible in javascript to have a variable that is not able to access out side the class’s functions, but is able to be accessed by classes that inherit it? I.E:

class1 has protected var x = 4;

class2 inherits class1;

class2.prototype.getVar = function(){return /* parent, uber, super, whatever */ this.x;};

var cl2 = new class2();

console.log(cl2.x) // undefined
console.log(cl2.getVar()) // 4

Answer 1

No. Prototypal inheritance is limited to properties of objects.

Variables within the constructor are only available to other code in that variable scope.

You could probably come up with something like…

function cls1() {
    var a = 'foo';
    this.some_func = function() {
        alert(a);
    };
}

function cls2() {
    cls1.apply(this, arguments);
    var cls1_func = this.some_func;

    var b = 'bar'

    this.some_func = function() {
        cls1_func.apply(this, arguments);
        alert(b);
    };
}

var x = new cls2;

x.some_func();  // alert "foo"  alert "bar"

---

Or to make it more specific to your pseudo code…

function class1() {
    var x = 4;
    this.getVar = function() {
        return x;
    };
}

function class2() {

    class1.apply(this, arguments);

    var cls1_get_var = this.getVar;

    this.getVar = function() {
        return cls1_get_var.apply(this, arguments);
    };
}

class2.prototype = Object.create( class1.prototype );

var cl2 = new class2;

console.log(cl2.x) // undefined
console.log(cl2.getVar()) // 4