Satya Prakash

Did you ever read about Optimization of website/blog through ordering styles and Scripts in head section? 
If you like your website load in browser as quickly as possible then you may have read in performance optimization tips that 
you should move all CSS files on top and script at last in HTML head section <head></head>.
How do you order those calls? If you are manually putting CSS and JavaScript files in head section (<head></head>), 
then you can do this very easily. Just modify once and optimization for this is over. 
What if you are using plugins and that are adding calls to JavaScript and CSS files dynamically. This is case of WordPress blog, 
where we use many plugins and those plugins add various Styles and Script files dynamically from wp_head() call.
If above lines, do not makes much sense to you then probably you have not 
read this documentation on <a href="http://code.google.com/speed/page-speed/docs/rtt.html#PutStylesBeforeScripts" rel="nofollow ugc">Google</a>.
The plugin will also collect different inline scripts to one place. Thus making the source code 
look better.
To check, if the plugin is doing anything or not, compare the Head section before and after 
activating the plugin.
(For reading more details discussion, follow the Plugin link on right side.)
<a href="https://profiles.wordpress.org/satya61229" rel="nofollow ugc">Author (satya61229) About page on WP</a>

Performance Optimization: Order Styles and Javascript

Ordering StyleSheet and JavaScript (external and inline) for performance optimization.

Tahir Yasin

This plugin lists all JavaScripts and Style sheets with a control field that lets you control CSS & JavaScript files to include only on the pages where you actually need them. The text field lets you use WP’s <a href="https://codex.wordpress.org/Conditional_Tags" rel="nofollow ugc">Conditional Tags</a>, or any general PHP code.
NOTE: The script logic you introduce is evaluated directly. Anyone who has permission to manage options will have the right to add any code, including malicious and possibly destructive code. There is an optional filter ‘script_logic_eval_override’ which you can use to bypass the EVAL with your own code if needed. (See <a href="other_notes/" rel="nofollow ugc">Other Notes</a>).
<h3>Writing Logic Code</h3>
The text in the ‘Logic’ field can be full PHP code and should return ‘true’ when you need the script to load. If there is no ‘return’ in the text, an implicit ‘return’ is added to the start and a ‘;’ is added on the end. (This is just to make single statements like is_home() more convenient.)
<h4>The Basics</h4>
Make good use of <a href="https://codex.wordpress.org/Conditional_Tags" rel="nofollow ugc">WP’s own conditional tags</a>. You can vary and combine code using:
<ul>
<li><code>!</code> (NOT) to reverse the logic, eg <code>!is_home()</code> is TRUE when this is NOT the home page.</li>
<li><code>||</code> (OR) to combine conditions. <code>X OR Y</code> is TRUE when either X is true or Y is true.</li>
<li><code>&&</code> (AND) to make conditions more specific. <code>X AND Y</code> is TRUE when both X is true and Y is true.</li>
</ul>
There are lots of great code examples on the WP forums, and on WP sites across the net. But the WP Codex is also full of good examples to adapt, such as <a href="https://codex.wordpress.org/Template_Tags/in_category#Testing_if_a_post_is_in_a_descendant_category" rel="nofollow ugc">Test if post is in a descendent category</a>.
<h4>Examples</h4>
<ul>
<li><code>is_home()</code> — just the main blog page</li>
<li><code>!is_page('about')</code> — everywhere EXCEPT this specific WP ‘page’</li>
<li><code>!is_user_logged_in()</code> — shown when a user is not logged in</li>
<li><code>is_category(array(5,9,10,11))</code> — category page of one of the given category IDs</li>
<li><code>is_single() && in_category('baked-goods')</code> — single post that’s in the category with this slug</li>
<li><code>strpos($_SERVER['HTTP_REFERER'], "google.com")!=false</code> — script to load when clicked through from a google search</li>
<li><code>is_category() && in_array($cat, get_term_children( 5, 'category'))</code> — category page that’s a descendent of category 5</li>
<li><code>global $post; return (in_array(77,get_post_ancestors($post)));</code> — WP page that is a child of page 77</li>
<li><code>global $post; return (is_page('home') || ($post->post_parent=="13"));</code> — home page OR the page that’s a child of page 13</li>
</ul>
Note the extra ‘;’ on the end where there is an explicit ‘return’.
<h3>The ‘script_logic_eval_override’ filter</h3>
Before the Script Logic code is evaluated for each script, the text of the Script Logic code is passed through this filter. If the filter returns a BOOLEAN result, this is used instead to determine if the script should load. Return TRUE to load.

Script Logic

Script Logic lets you control on which pages scripts and style sheets load using WP's conditional tags.

Performance Optimization: Order Styles and Javascript vs Script Logic