method/function inside object method javascript

Question

Hey guys I've just started using javascript's prototype and I was wondering if it's possible, and if so, how to call a function inside a method eg:

obj = function(test){
this.test=test;
}

obj.prototype.a = function(){
    var x = this.test;

    function b(){
        alert(x);
    }

    function c(){
    console.log(x);
    }
}

var foo = new obj();
foo.a.b();

So, could I access function b inside obj.a without calling function c ie I want to be able to call a and have it call both functions inside it, but also be able to just call b or c if I need to?

I know I could just put these in separate methods outside of a, but I thought I'd ask the question.

Cheers.

Tip: even if you are just tweaking stuff for learning purposes, give meaningful name to methods and variables. — moonwave99
– moonwave99, Commented Jul 7, 2013 at 11:45
I have done in my code, I just wanted to keep it simple for the question. Cheers :) — Rwd
– Rwd, Commented Jul 7, 2013 at 11:46
Should there be "return this" at the end of function a so that foo.a().b() to work? — Wand Maker
– Wand Maker, Commented Jul 7, 2013 at 11:49
@WandMaker: That wouldn't make any difference. Nothing in a makes b available to the outside world. Now, if a had return {b: b}, then foo.a().b() would work. Or if a had return b; then foo.a()() would work. — T.J. Crowder
– T.J. Crowder, Commented Jul 7, 2013 at 11:50
@TJ I see. Its kind of tricky to visualize what the author is trying to achieve though — Wand Maker
– Wand Maker, Commented Jul 7, 2013 at 11:53

Quentin · Accepted Answer · 2013-07-07 11:46:18Z

2

b is scoped to the anonymous function in which it is declared. There is no way to access from outside that function without changing that function to expose it.

You can call a because it is a property of the object prototype (it isn't stored in a scoped variable). b and c are not exposed at all. The way you have written the code is how people usually create private methods in JavaScript.

answered Jul 7, 2013 at 11:46

Quentin

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2 Comments

Rwd Over a year ago

thanks, @Quentin. I just edited the question to see I can change the way I've written it. Could I add a method to a method basically?

Quentin Over a year ago

A method is a function. A function is an object. Objects can be given (more or less) arbitrary properties, so yes (but not from inside the function unless you want it to be available only after it is called). obj.prototype.a.b = function () {}

Forbesmyester · Accepted Answer · 2013-07-07 11:52:36Z

1

You could alter your code a bit to make it possible, but I suspect what you really want is to be able still to get the value of x when you call b from outside... Am I right?

Have you perhaps considered making a another instance in it's own right? I'm assuming your code is non-trivial enough to make this worth while...

answered Jul 7, 2013 at 11:52

Forbesmyester

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1 Comment

Rwd Over a year ago

Kind of...I want to be able to call a and have it call both functions inside it, but also be able to just call b or c if I need to.

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