WordPress: Add Manual Excerpt Word Counter

functions.php

add_action( 'admin_head-post.php', 'we_excerpt_count_js' );
add_action( 'admin_head-post-new.php', 'we_excerpt_count_js' );
/**
 * Add Manual Excerpt Word Counter in Posts
 * 
 */
function we_excerpt_count_js() {
	echo '<script>jQuery(document).ready(function(){
		jQuery("#postexcerpt .handlediv").after("<div style=\"position:absolute;top:0px;right:5px;color:#666;\"><small>Excerpt length: </small><input type=\"text\" value=\"0\" maxlength=\"3\" size=\"3\" id=\"excerpt_counter\" readonly=\"\" style=\"background:#fff;\"> <small>word(s).</small></div>");
		jQuery("#excerpt_counter").val(jQuery("#excerpt").val().split(/\S+\b[\s,\.\'-:;]*/).length - 1);
		jQuery("#excerpt").keyup( function() {
			jQuery("#excerpt_counter").val(jQuery("#excerpt").val().split(/\S+\b[\s,\.\'-:;]*/).length - 1);
   		});
	});</script>';
}