Javascript using nested functions as an object to access

Question

I wrote a program like this:

function a(x,y,z) {
        function b(foo,bar) {};
        function c(foo,bar) {};
        function d(foo,bar) {};
        function e(foo,bar) {};
        function f(foo,bar) {};
}

I call the function this way: for(var i=0; i<5; i++) { charts[i] = a(x[i],y[i],z[i])}

x,y and z are global arrays of length 5 and some properties.

Now, the loop gets executed before page load and all the functions for each of the array is also executed as expected (There are event listeners bound to elements in these functions)

Let's say I want to access some local variables from b,c,d,e or f "after" page load, when an event is invoked, how do i do it? I'm talking about "scope" here I think.

Do I have to make the whole thing an object?

Also, there are local variables inside b,c,e and f (locally declared and not using "this"). There are also variables inside of a which is accessed by b,c,d,e and f (Again, locally declared, not using "this")

Thanks!

You cannot access local variables from outside of the scope where they were created. You have to either expose them to the global scope or have getter functions within your local scope. — Amberlamps
– Amberlamps, Commented Jul 12, 2013 at 12:03

Mke Spa Guy · Accepted Answer · 2013-07-13 17:07:44Z

2

You can simple create a new object inside a and return that object.

var a = function (x, y, z) {
    var result = {};
    var outerVal = x;
    result.b = function (foo, bar) { return foo + bar; };
    result.c = function (foo, bar) { return outerVal + result.g + z};  //closure
    result.d = function (foo, bar) { };
    result.e = function (foo, bar) { };
    result.f = function (foo, bar) { };
    result.g = y;
    //If you want to execute the functions you can do so
    result.bValue = result.b(x, y);
    result.c(y, z);
    return result;
};

var anA = a(1, 2, 3);
console.log(anA.bValue); //3
console.log(anA.b(2, 5)); //7
console.log(anA.c()); //6

edited Jul 13, 2013 at 17:07

answered Jul 12, 2013 at 12:25

Mke Spa Guy

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2 Comments

KaushikTD Over a year ago

Okay so, what if I create a result.g variable inside a. Can I access result.g inside result.b?

Mke Spa Guy Over a year ago

@TaushikTD Yes you can. You can also access local vars and parameters passed into a. This is called closure and is a powerful feature of JavaScript. See my edit with result.c(). (Note: all parameters in JS are optional. anA.c() is legal and foo and bar will be null)

Jon · Accepted Answer · 2013-07-12 12:20:53Z

What Amberlamps said, you cannot access local variables from outside of the scope they are created, meaning your function a cannot "see" any variables created in b, c, d, e, f. You could either create some global variables (global to b, c, d, e and f) or you could consider writing a closure:

var something = (function () {

    var globalOne = null,
        globalTwo = null;
        //...

    return {

        a: function (x, y, z) {
            something.b(foo, bar);
            something.c(foo, bar);
        },

        b: function (foo, bar) {

        },

        c: function (foo, bar) {

        }

        // etc.

    };

}());

This could be a little overkill for what you're trying to do, but what's nice with the closure is that your globals globalOne and globalTwo cannot be modified by the client.

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