Is it possible to reference object within the same object?

Question

I've been messing around with jQuery plugin code and I'm trying to put all of my common variables into a single object for easy access. I have included a few examples below on how I've done this, but I'm wondering how others deal with this problem.

Lets say I have this

var x = function(options){ var defaults = { ulist : $('ul#list'), listLen : $('ul#list').children().length } $.extend(options, defaults); // do other stuff }

What I'm trying to do is use the ulist object in as a base, then find the number of li's

I guess I could do this:

var x = function(options){ var defaults = { ulist : $('ul#list'), listLen : 0 } defaults.listLen = defaults.ulist.children().length; $.extend(options, defaults); // do other stuff }

or this:

var x = function(options){ var defaults = { ulist : $('ul#list') }; var defaults2 = { listLen : defaults.ulist.children().length } $.extend(defaults, defaults2); $.extend(options, defaults); // do other stuff }

The above code samples are just thrown together, and only meant to get the idea across to you. Anyway, is there a better way to do this?

@stereofrog: That is what I was looking for, thanks! Would you add it as an answer so I can accept it please? — Mottie
– Mottie, Commented May 13, 2010 at 19:28
if you're going to take the function approach in order to get the current length, I'd still add the function outside of the defaults object, so you can place the function call operator () at the end, letting you can access defaults.listLen like a property (like calling .length on a jQuery object). I'll update my answer, but feel free to accept stereofrog's answer since he pointed to that method. — user113716
– user113716, Commented May 13, 2010 at 19:49

user187291 · Accepted Answer · 2011-10-07 01:44:17Z

I would say this version that you posted, but no need to initialize listLen to 0.

var x = function(options){ var defaults = { ulist : $('ul#list'), listLen : 0 // Remove this line } defaults.listLen = defaults.ulist.children().length; $.extend(options, defaults); // do other stuff }

EDIT:

Your second solution would work too, but no need to do two calls to $.extend(). It can accept more than one object.

$.extend(options, defaults, defaults2);

Your first solution still seems better.

EDIT:

(As pointed to, you can use a function. Although I'd still assign the function outside the initialization of the defaults object, so you can add the function call operator () at the end, and call it like a property.

var x = function(options){ var defaults = { ulist: $('ul#list') } defaults.listLen = function() {return defaults.ulist.children().length}(); }

Now you can access defaults.listLen like a property and get the result of the function call, sort of like calling .length on a jQuery object.

Thanks Patrick, you are right, I'll use the method in your original answer to minimize the number of function calls. Thanks for all the feedback!

Sean O · Accepted Answer · 2010-05-13 17:50:49Z

The jQuery plugin development pattern by Mike Alsup is a few years old, but has aged well, and is still a great starting point for plugin development.

http://www.learningjquery.com/2007/10/a-plugin-development-pattern

Thank you for your response, but it doesn't answer which method is best or if the examples above are my only options.

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