Comments on: Issues with Crockford’s JavaScript conventions

By: TJ Singleton

TJ Singleton — Wed, 08 Sep 2010 01:43:48 +0000

I realize this is an old post, but the title caught my eye. When you use a function declaration, it is ‘hoisted’ to the top of the current scope by the interpreter for you. Crockford’s convention is to predefine function expressions.

Here is a good article I just found that demonstrates this behavior: http://www.adequatelygood.com/2010/2/JavaScript-Scoping-and-Hoisting. I actually found it out watching Crockford’s video series on javascript, http://developer.yahoo.com/yui/theater/video.php?v=crockonjs-3.

By: OliverB

OliverB — Tue, 17 Mar 2009 06:51:55 +0000

Crying out for a Haskell where clause… it’s just syntax but it lets you put local declarations at the end of code rather than before.

function foo = blah doStuffLater where
doStuffLater = ….

By: Chris

Chris — Tue, 10 Mar 2009 21:01:09 +0000

@Barry:

At least in JavaScript all functions are closures anyway. Since “function foo() { … }” means the same thing as “var foo = function () { … };” there will be no overhead if you predeclare a variable. Still ugly though.

I guess we just have a stylistic difference when it comes to how we read code.

By: RichB

RichB — Tue, 10 Mar 2009 09:22:16 +0000

Declaring variables is aimed at preventing global namespace polution. If you’re not polluting the global namespace with your functions, then you need not worry.

By: Barry Kelly

Barry Kelly — Tue, 10 Mar 2009 06:59:56 +0000

With mutual recursion, there’s no choice but to live with an undeclared symbol, unless one is to use explicit closures held in declared variables.

However, for your callback example, I personally prefer the style where the callback is declared before it is used. Perhaps it is a preference that has stayed in my mind since I used to program in Pascal, or its related to my knowledge of how compilers work, but I do like to see symbols defined before they are used as I read forward through the code.