wp_enqueue_script() WP 2.1.0

Adds a script (JavaScript file) to the page.

It is important to use this function to add JS files because with it you can merge several JS files into one without further problems. Also, it helps you to get rid of script conflicts when the dependent script is connected after the one from which it depends.

The function adds a script only if it has not been added yet and if the other scripts on which it depends are registered. Dependent scripts are added (connected) automatically.

IMPORTANT! This function may not work if wp_head() and wp_footer() functions are not used in your theme. It's because the scripts are loaded on actions (hooks) created by these functions.

If the script is already registered with wp_register_script() then you can enqueue it by its identifier ($handle).

// jquery is registered in WP by default.
// So you can enqueue it just by its identifier:
wp_enqueue_script('jquery');

If the script isn't registered, then you can register and enqueue it just with this function.

 wp_enqueue_script('newscript', get_template_directory_uri() . '/js/custom_script.js');

Since version 3.3 this function can be used during the page generation. In this case, the enqueued script will be loaded in the footer of the page when the hook wp_footer is called.

Usually the function is hooked on one of these actions:

wp_enqueue_scripts — for front-end;
admin_enqueue_scripts — for admin-panel;
login_enqueue_scripts — for login page (wp-login.php).

If you want to enqueue the script on some condition, e.g. , use wp_script_add_data()

Contents:

Usage
Examples
jQuery in no-conflict mode
Default WordPress scripts:
Notes

Is the basis for: the_custom_header_markup(), wp_enqueue_code_editor()

Works based on: WP_Dependencies::enqueue()

No Hooks.

Return

Nothing (null).

Usage

wp_enqueue_script( $handle, $src, $deps, $ver, $in_footer );

$handle(string) (required)

Name of the script. Should be unique. In lowercase.

If the string contains a question mark (?): scriptaculous?v=1.2, then the preceding part will be the name of the script, and all that text after the question mark will be added to the URL as request parameters. So you can, for example, specify the version of the script.

$src(string)

Full URL of the script, or path of the script relative to the WordPress root directory. For example:
http://example.com/wp-content/themes/my-theme/my-theme-script.js.

This option is only needed when the script is not registered and WordPress is not yet aware of it and its path. see wp_register_script().

There's no need to specify a hardcoded path, use the following functions:

plugins_url() - for plugins and
get_template_directory_uri() - for themes.

External domains can be specified with implicit protocol //example.com/js/their-script.js

See below the list of all registered scripts by default (like jquery).

Default: ''

$deps(array)

An array of registered script handles this script depends on. Scripts that must be loaded before this one.
Default: array()

$ver(string/true/false/null)

String specifying script version number. The version is added to the URL as a query string for cache busting purposes.

If set to false, the current WordPress version will be used.

If set to null, version adding will be skipped.

Default: false

$in_footer(true/false)

Whether to enqueue the script in the footer?

Typically, a script is included in the <head> of the document, if set to true, the script will be included before the </body> tag (where the wp_footer() template tag is called).

If due to the dependence on other scripts, there is no way to connect the current script in the footer, this parameter will be ignored.

For clear code, you may specify any string instead of true, for example, you can use 'in_footer'.

Default: false

Examples

#1 Replace the default script

For example if you want to replace the default jquery script with a CDN-version, add this code to the functions.php:

add_action( 'wp_enqueue_scripts', 'my_scripts_method', 11 );
function my_scripts_method() {
	wp_deregister_script( 'jquery' );
	wp_register_script( 'jquery', 'http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js' );
	wp_enqueue_script( 'jquery' );
}

Using the wp_enqueue_scripts filter (instead of init as recommended on some resources), we avoid registering an alternative version of jQuery on the dashboard, what (among other things) reduces the risk of disruption of the wp-editor.

#2 Enqueue a default script

// For frontend of the site
add_action( 'wp_enqueue_scripts', 'my_scripts_method' ); 
function my_scripts_method() {
	wp_enqueue_script( 'scriptaculous' );            
}

#3 Register and enqueue a custom script

add_action( 'wp_enqueue_scripts', 'my_scripts_method' );
function my_scripts_method() {
	$script_url = plugins_url( '/js/newscript.js', __FILE__ );
	wp_enqueue_script('custom-script', $script_url, array('jquery') );
}

#4 Enqueue a script only for specific types of pages

For example you need conditional tags for loading script scriptaculous. You can use hook wp because conditionals tags available after it.

add_action( 'wp', 'add_my_script_where_it_necessery' );
function add_my_script_where_it_necessery(){
	if( is_single() )
		add_action( 'wp_enqueue_scripts', 'my_scripts_method' );
}
function my_scripts_method() {
	$script_url = plugins_url( '/js/newscript.js', __FILE__ );
	wp_enqueue_script( 'newscript', $script_url, ['scriptaculous'] );
}

#5 Enqueue a script that depends on a default script

Specify the name of the dependency in the third argument.

add_action('wp_enqueue_scripts', 'my_scripts_method');
function my_scripts_method() {
	wp_enqueue_script('custom-script',
		get_template_directory_uri() . '/js/custom_script.js',
		array('jquery')
	);
}

#6 Loading plugin scripts only on its pages

add_action( 'admin_menu', 'my_plugin_admin_menu' );
function my_plugin_admin_menu() {
	// Register plugin page
	$page = add_submenu_page(
		'edit.php',                     
		__( 'My plugin', 'myPlugin' ),  
		__( 'My plugin', 'myPlugin' ),  
		'manage_options',               
		'my_plugin-options',            
		'my_plugin_manage_menu'         
	);

	// Connect to a needed hook using the plugin page identifier 
	add_action( 'load-' . $page, 'my_plugin_admin_scripts' );
}

// This function will be called only on the page of the plugin
function my_plugin_admin_scripts() {
	wp_enqueue_script( 'my-plugin-script', plugins_url('/script.js', __FILE__) );
}

function my_plugin_manage_menu() {
	// page code
}

#7 Dynamic file version detection

To change file URL when the file content changed in order to disable browser cache, you can specify file version dynamically base on file modification time (filemtime):

add_action('wp_enqueue_scripts', 'my_scripts_method');
function my_scripts_method() {
	wp_enqueue_script( 'custom-script',
		get_template_directory_uri() . '/js/custom_script.js',
		[ 'jquery' ],
		filemtime( get_theme_file_path('js/custom_script.js') )
	);
}

filemtime() performance is very high - on SSD disk 0.5 sec for 50K iterations - it's very fast!

#8 Remove a version of the script or style from the URL

When registering a script, it gets a version (the current version of WordPress, by default): /wp-includes/css/dashicons.min.css?ver=4.9. You can remove it:

// Removing all versions of all scripts (and styles):
add_filter( 'script_loader_src', '_remove_script_version' );
add_filter( 'style_loader_src', '_remove_script_version' );
function _remove_script_version( $src ){
	$parts = explode( '?', $src );
	return $parts[0];
}

Remove only WordPress versions:

add_filter( 'script_loader_src', 'hb_remove_wp_version_from_src' );
add_filter( 'style_loader_src', 'hb_remove_wp_version_from_src' );
function hb_remove_wp_version_from_src( $src ) {
	 global $wp_version;
	 parse_str( parse_url( $src, PHP_URL_QUERY ), $query );
	 if ( ! empty($query['ver']) && $query['ver'] === $wp_version ) {
		  $src = remove_query_arg('ver', $src);
	 }
	 return $src;
}

jQuery in no-conflict mode

WordPress loads jQuery in «no conflict» mode by default. It was made for compatibility with other libraries that can be loaded as well.

In «no-confict» mode $ shortcut is not available. For example, this code will not work:

$(document).ready( function(){
	 $('#element') ...
});

You should tweak it a bit:

jQuery(document).ready( function($){
	$('#element') ...
});

Pay attention to the $ sign which is passed to the function - doing so we can use $ sign in the js code.

If you don't want to wait for "DOM ready" action, you can invoke function expression immediately:

(function($) {

	// Here $ refers to jQuery. So you can use $.

})(jQuery);

Default WordPress scripts:

Script Name	ID	Dependency
Image Cropper	Image cropper (not used in core, see jcrop)
Jcrop	jcrop
SWFObject	swfobject
SWFUpload	swfupload
SWFUpload Degrade	swfupload-degrade
SWFUpload Queue	swfupload-queue
SWFUpload Handlers	swfupload-handlers

jQuery	jquery	json2 (for AJAX calls)
jQuery Form	jquery-form	jquery
jQuery Color	jquery-color	jquery
jQuery Masonry	jquery-masonry	jquery
Masonry (native Javascript)	masonry
jQuery UI Core	jquery-ui-core	jquery
jQuery UI Widget	jquery-ui-widget	jquery
jQuery UI Accordion	jquery-ui-accordion	jquery
jQuery UI Autocomplete	jquery-ui-autocomplete	jquery
jQuery UI Button	jquery-ui-button	jquery
jQuery UI Datepicker	jquery-ui-datepicker	jquery
jQuery UI Dialog	jquery-ui-dialog	jquery
jQuery UI Draggable	jquery-ui-draggable	jquery
jQuery UI Droppable	jquery-ui-droppable	jquery
jQuery UI Menu	jquery-ui-menu	jquery
jQuery UI Mouse	jquery-ui-mouse	jquery
jQuery UI Position	jquery-ui-position	jquery
jQuery UI Progressbar	jquery-ui-progressbar	jquery
jQuery UI Selectable	jquery-ui-selectable	jquery
jQuery UI Resizable	jquery-ui-resizable	jquery
jQuery UI Selectmenu	jquery-ui-selectmenu	jquery
jQuery UI Sortable	jquery-ui-sortable	jquery
jQuery UI Slider	jquery-ui-slider	jquery
jQuery UI Spinner	jquery-ui-spinner	jquery
jQuery UI Tooltips	jquery-ui-tooltip	jquery
jQuery UI Tabs	jquery-ui-tabs	jquery
jQuery UI Effects	jquery-effects-core	jquery
jQuery UI Effects - Blind	jquery-effects-blind	jquery-effects-core
jQuery UI Effects - Bounce	jquery-effects-bounce	jquery-effects-core
jQuery UI Effects - Clip	jquery-effects-clip	jquery-effects-core
jQuery UI Effects - Drop	jquery-effects-drop	jquery-effects-core
jQuery UI Effects - Explode	jquery-effects-explode	jquery-effects-core
jQuery UI Effects - Fade	jquery-effects-fade	jquery-effects-core
jQuery UI Effects - Fold	jquery-effects-fold	jquery-effects-core
jQuery UI Effects - Highlight	jquery-effects-highlight	jquery-effects-core
jQuery UI Effects - Pulsate	jquery-effects-pulsate	jquery-effects-core
jQuery UI Effects - Scale	jquery-effects-scale	jquery-effects-core
jQuery UI Effects - Shake	jquery-effects-shake	jquery-effects-core
jQuery UI Effects - Slide	jquery-effects-slide	jquery-effects-core
jQuery UI Effects - Transfer	jquery-effects-transfer	jquery-effects-core
MediaElement.js (WP 3.6+)	wp-mediaelement	jquery
jQuery Schedule	schedule	jquery
jQuery Suggest	suggest	jquery

ThickBox	thickbox
jQuery HoverIntent	hoverIntent	jquery
jQuery Hotkeys	jquery-hotkeys	jquery
Simple AJAX Code-Kit	sack
QuickTags	quicktags
Iris (Colour picker)	iris	jquery
Farbtastic (deprecated)	farbtastic	jquery
ColorPicker (deprecated)	colorpicker	jquery
Tiny MCE	tiny_mce
Heartbeat	heartbeat	jquery
Autosave	autosave
WordPress AJAX Response	wp-ajax-response
List Manipulation	wp-lists
WP Common	common
WP Editor	editorremov
WP Editor Functions	editor-functions
AJAX Cat	ajaxcat
Admin Categories	admin-categories
Admin Tags	admin-tags
Admin custom fields	admin-custom-fields
Password Strength Meter	password-strength-meter
Admin Comments	admin-comments
Admin Users	admin-users
Admin Forms	admin-forms
XFN	xfn
Upload	upload
PostBox	postbox
Slug	slug
Post	post
Page	page
Link	link
Comment	comment
Threaded Comments	comment-reply
Admin Gallery	admin-gallery
Media Upload	media-upload
Admin widgets	admin-widgets
Word Count	word-count
Theme Preview	theme-preview
JSON for JS	json2
Plupload Core	plupload
Plupload All Runtimes	plupload-all
Plupload HTML4	plupload-html4
Plupload HTML5	plupload-html5
Plupload Flash	plupload-flash
Plupload Silverlight	plupload-silverlight
Underscore js	underscore
Backbone js	backbone

This is not a full list. To get full list, see the global variable $GLOBALS['wp_scripts'] in the admin.

Or see code of wp_default_scripts() function. This function registers all default scripts.

Notes

Since version 3.5, WordPress has a new convention for minified scripts and styles. Before that version minified scripts and styles had extensions .js and .css, respectively; non-minified .dev.js and .dev.css. Now minified files have .min.js and .min.css extensions; non-minified — just .js and .css.

Code of wp enqueue script: `wp-includes/functions.wp-scripts.php` ^{WP 5.2.2}

<?php
function wp_enqueue_script( $handle, $src = '', $deps = array(), $ver = false, $in_footer = false ) {
	$wp_scripts = wp_scripts();

	_wp_scripts_maybe_doing_it_wrong( __FUNCTION__ );

	if ( $src || $in_footer ) {
		$_handle = explode( '?', $handle );

		if ( $src ) {
			$wp_scripts->add( $_handle[0], $src, $deps, $ver );
		}

		if ( $in_footer ) {
			$wp_scripts->add_data( $_handle[0], 'group', 1 );
		}
	}

	$wp_scripts->enqueue( $handle );
}

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