wp_enqueue_script(), using LABJS. The result is a significant optimization of loading time.
wp_localize_script(), js in header, in footer…) and works with all well coded plugins.
If a plugin or a theme is not properly enqueuing scripts, your site may not work. Check this page: Function Reference/wp_enqueue_script on WordPress Codex.
We performed a range of tests to determine the potential benefit of loading time. On wabeo we executed webwait (150 calls by test). Result is this plugin could improve your loading time by 25%!!
More information in the Screenshots section.
Source from: WordPress.org