We need to know how the script is being enqueued, but if it’s done right, you will be able to remove that .js file using wp_dequeue_script.
How to correctly enqueue scripts
function my_register_script()
//Registers a script to be enqueued later
wp_register_script('script-handle', plugins_url('script.js', __FILE__));
}
add_action( 'wp_enqueue_scripts', 'my_register_script', 10);
function my_enqueue_script(){
//Enqueue the script
wp_enqueue_script('script-handle');
}
//hook to another action
add_action('other_action', 'my_enqueue_script', 10);
The wp_register_script register the script to be used, passing a $handle (id) and the script $src (url to the script). The wp_enqueue_script adds that script to our page.
It can also happen that the wp_register_script is not used. In that case, the $src is passed to the wp_enqueue_script like this.
wp_enqueue_script('script-handle', plugins_url('script.js', __FILE__));
How to remove a correctly registered script
If the script is enqueued correctly, then you can remove it from your functions.php passing the $handle to wp_dequeue_script.
wp_dequeue_script('script-handle');
Keep in mind that this function should be used after the script has been enqueued, so you should check to which action the wp_enqueue_script is hooked and run the wp_dequeue_script later, hooking it to the same action but with a higher priority.
Following the same example, the wp_enqueue_script is hooked to an action with a $priority of 10, so you should hook the dequeue with a bigger priority
function my_dequeue_script(){
//Removes the enqueued script
wp_dequeue_script('script-handle');
}
//hook to another action
add_action('other_action', 'my_dequeue_script', 11);
Where 11 in the add_action function is the $priority (Bigger means later execution)
Do not forget that there may be some scripts that depends of the script you are dequeuing. If thats the case, those scripts won’t load.