How to add if lt IE9 conditional scripts to functions.php

Question

I am trying to enqueue a conditional javascript file for lt IE9 in the functions.php file (in Wordpress). For anyone viewing the website in IE9 this script will be triggered. Is what I have below anywhere near correct? That jQuery $ will cause problems because of Wordpress runs in nonConflict mode. But this was the only answer I have found. I already have multiple style sheets and scripts running in my functions.php file with no bother.

global $wp_scripts;
wp_register_script( 'ie_js', '/js/ie.js,  array(),  '' );
$wp_scripts->add_data( 'ie_js', 'conditional', 'lt IE 9' );

Answer 1

Yes, that looks broadly correct (barring a missing '). That isn't a jQuery $, so shouldn't cause any problems - the dollar prefix here is the usual convention for PHP variable names and won't make it into the included script.

Or if I've misunderstood and you meant your ie.js script assumes jQuery is $ then you can solve that by wrapping it in a self-executing function which defines a scope where $ = jQuery, e.g.

(function($){
    ...
})(jQuery);

Also as of 4.2 there's a helper function wp_script_add_data so you can write instead:

wp_register_script( 'ie_js', '/js/ie.js',  array(),  '' );
wp_script_add_data( 'ie_js', 'conditional', 'lt IE 9' );