Using wp_is_mobile() in WordPress to detect mobile users (phones and tablets)

script.js

jQuery( document ).ready( function($) {
 
    if ( $( "body" ).hasClass("wp-is-mobile"){
        /* Do javascript for mobile */
    }
    else{
        /* Do javascript for non-mobile */
    }
 
});

wp_is_mobile_usage.php

<?php

if ( wp_is_mobile() ) :

    /* do stuff for mobile user */
    
else :

    /* do stuff for non mobile user */

endif;

/* Filter body class */
add_filter('body_class','my_theme_body_class');
 
/**
 * Add Mobile Body Class "wp-is-mobile" for mobile and "wp-is-not-mobile" for non-mobile device
 */
function my_theme_body_class( $classes ){
    if ( wp_is_mobile() ) :
        $classes[] = 'wp-is-mobile';
    else :
        $classes[] = 'wp-is-not-mobile';
    endif;
    return $classes;
}

?>

Be aware this technique won't help if you use full page caching.