jQuery(function($){

$(".foo"); // Use like you would normally.

});

This does the following.

1) Encapsulates the code cleanly so as not to leak into the dom.
2) Waits for the DOM to be ready before executing
3) Executes the function passing the jQuery object in as $

This way $ doesn't exist outside this function, but does inside it, immeasurably helpful.

Maybe Prototype has some other way to accomplish this sort of thing; I've not used it.

Then if you want the DOM node you can always get it in the manner you mentioned; but like Dan said, I rarely find myself needing to do that, while I am constantly chaining methods.

I know about jQuery's $() function, but it returns jQuery, not a DOM node. There's a difference. As Dan points out, it also requires supplying a hash in the string, rather than just the bare ID. I am running in noConflict mode to ensure that any lingering $() calls (to Prototype) are fast-fail, but that's not a requirement of Prototype's class framework – it's $ agnostic.

Like I said at the end of the post, I'm in the conversion process at the moment, so the differences are glaring, regardless of their actual effect. The more significant issue is definitely the performance (and it's ramifications), since that won't go away as the conversion comes to a close.

function $$(id){ return jQuery("#"+id)[0]; }

Personally, I rarely deal with raw DOM elements anymore. Also, we'll getting used to the CSS-style selectors was something I wasn't fond of at first (since I thought have to write "#id" was a bit of a PITA,) I've since come to like it. I find it makes switching between writing CSS rules and jQuery much easier and it's more clear.

You mentioned that you're still using the Prototype class framework in conjunction with jQuery, so that's why you may need to use the more verbose jQuery call.

There is a $ function in jQuery, which is just the same as the jQuery function. Not sure what would make you think the $ function didn't exist. I've been using it for months!

There's a big advantage of jQuery over Prototype but it's very situational. If you're writing a JS library which uses jQuery, you obviously don't want to interfere with the $ (and perhaps jQuery) function if your client is using Prototype, another version of jQuery, or has their own implementation of either of these functions. jQuery provides the noConflict method which will let you put the $ function into your own variable and put whatever was in there originally, back in.

Say a client is using the $ function Prototype, then I go include jQuery using my library. jQuery can put Prototype back into window.$ and return a reference to jQuery's $ function for you to put into your own variable for use internally by your own library. So instead of doing $('#theId'), you'd do jq('#theId'), for example.

Like I said, it's very situational, but it's something jQuery has which Prototype doesn't (as far as I can tell so far).

Hope this makes sense!

George.

$(function(){
reference = $('#myelement');
});

as an id should be unique you don't need to reference the first element in the array.