Peter Raschendorfer

The Smart JavaScript Auto Loader Plugin allows you to load additional JavaScript files without the need to change files in the theme directory
<h3>Retired Plugin</h3>
Development, maintenance and support of this plugin has been retired in october 2023. You can use this plugin as long as is works for you.
There will be no more updates and I won’t answer any support questions. Thanks for your understanding.
Feel free to fork this plugin.
<h3>Usage</h3>
To load additional JavaScript files just put them into a directory named jsautoload. This directory can be placed in three different locations that are loaded in the following order:
<ul>
<li>Child Theme dependent (if using a Child Theme) : in the Child Theme’s directory</li>
<li>Theme dependent : in the Theme’s directory</li>
<li>Theme independent : in the wp-content directory</li>
</ul>
Only files with extension .js are added, all other files are ignored. Subdirectories can be used and will also be scanned. To ignore a complete directory (including all subdirectories) name the directory beginning with an underscore (_). The files are added in alphabetical order. Directories always are added after files.
To load one ore more JavaScript files at the end of your HTML file just place them into a directory named footer. To add the files to the footer of your theme it is required to call wp_footer() in your footer.php.
<h3>Plugin Privacy Information</h3>
<ul>
<li>This plugin does not set cookies</li>
<li>This plugin does not collect or store any data</li>
<li>This plugin does not send any data to external servers</li>
</ul>

Smart JavaScript Auto Loader

Brian Zeligson

This plugin uses the wp_print_scripts action hook, as opposed to output buffering and regex used by alternative implementations.
The downside of this method is that only scripts loaded via wp_enqueue_script will be affected by the plugin, the upside is better 
performance by avoiding output buffering on every page load.
The plugin will preserve any localizations added via wp_localize_script, and uses the first parameter passed to wp_enqueue_script 
as the label for the script in the head.js call. For example,
<pre><code>wp_enqueue_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js');
</code></pre>
would show up as
<pre><code>head.js({"jquery": "https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"});
</code></pre>
This allows you to run callbacks when specific scripts are ready, such as
<pre><code>head.ready('jquery', function() {
 //do something when jquery is loaded
});
</code></pre>
For more on HeadJS usage, see http://headjs.com/

WP HeadJS

Uses HeadJS to load your enqueued scripts asynchronously, in parallel, executing them in order.

Smart JavaScript Auto Loader vs WP HeadJS