Multiple javascript/css files: best practices?

I have about 7 Javascript files now (thanks to various jQuery plugins) and 4-5 CSS files. I'm curious as to what's the best practice for dealing with these including where in the document they should be loaded? YSlow tells me that Javascript files should be--where possible--included at the end. The end of the body? It mentions that the delimeter seems to be whether they write content. All my Javascript files are functions and jQuery code (all done when ready()) so that should be OK.

So should I include one CSS and one Javascript file and have those include the rest? Should I concatenate all my files into one? Should I put Javascript my

I would suggest using [PHP Minify][1], which lets you create a single HTTP request for a group of JS or CSS files. Minify also handles GZipping, Compression, and HTTP Headers for client side caching.

Edit: Minify will also allow you to setup the request so that for different pages you can include different files. For example a core set of JS files along with custom JS code on certain pages or just the core JS files on other pages.

While in development include all the files as you normally would and then when you get closer to switching to production run minify and join all the CSS and JS files into a single HTTP request. It's really easy to setup and get working with.

Also yes, CSS files should be set in the head, and JS files served at the bottom, since JS files can write to your page and can cause massive time-out issues.

Here's how you should include your JS files:

</div> <!-- Closing Footer Div -->
<script type="application/javascript" src="http://jqueryjs.googlecode.com/files/jquery-1.3.1.min.js"></script>
</body>
</html>

Edit: You can also use [Cuzillion][2] to see how your page should be set up.

[1]: http://code.google.com/p/minify/ "Google Code: Minify" [2]: http://stevesouders.com/cuzillion/ "Cuzillion"

Here's what I do: I use up to two JavaScript files and generally one CSS file for each page. I figure out which JS files will be common across all of my pages (or enough of them so it's close - the file containing jQuery would be a good candidate) and then I concatenate them and minify them using jsmin-php and then I cache the combined file. If there are any JS files left over that are specific to that one page only, I concatenate, minify, and cache them into a single file as well. The first JS file will be called over a number of pages, the second only on that one or maybe a few.

You can use the same concept with CSS if you like with css-min, though I find I usually only use one file for CSS. One thing extra, when I create the cache file, I put in a little PHP code in the beginning of the file to serve it as a GZipped file, which is actually where you'll get most of your savings anyways. You'll also want to set your expiration header so that the user's browser will have a better chance of caching the file as well. I believe you can also enable GZipping through Apache.

For the caching, I check to see if the file creation time is older than the amount of time that I set. If it is, I recreate the cache file and serve it, otherwise I just get the existing cached file.

You haven't explicitly said that you've got access to a server-side solution, but assuming you do, I've always gone with a method involving using PHP to do the following:

jquery.js.php:

<?php
$jquery = ($_GET['r']) ? explode(',', $_GET['r']) : array('core', 'effects', 'browser', 'cookies', 'center', 'shuffle', 'filestyle', 'metadata');
foreach($jquery as $file)
 {
echo file_get_contents('jquery.' . $file . '.js');
 }
?>

With the snippet above in place, I then call the file just like I normally would:

<script type="text/javascript" src="jquery.js.php"></script>

and then if I'm ever aware of the precise functionality I'm going to need, I just pass in my requirements as a query string (jquery.js.php?r=core,effects). I do the exact same for my CSS requirements if they're ever as branched.

I would not recommend using a javascript based solution (like PHP Minify) to include your css as your page will become unusable if the visitor has javascript disabled.

The idea of minifying and combining the files is great.

I do something similar on my sites but to ease development I suggest some code which looks like this:

if (evironment == production) {
  echo "<style>@import(/Styles/Combined.css);</style>"
} else {
  echo "<style>@import(/Styles/File1.css);</style>"
  echo "<style>@import(/Styles/File2.css);</style>"
}

This should let you keep your files separate during dev for easy management and use the combined file during deployment for quicker page loads. This assumes you have the ability to combine the files and change variables as part of your deploy process.

Definitely look into including your js at the bottom and the css at the top as per YUI recommendations as keeping the JS low has a tangible affect on the appearance of the rest of the page and feels much faster.

I also tend to copy+paste all of my jquery plugins into a single file: jquery.plugins.js then link to

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js">

for the actual jquery library.