We process a lot of JavaScript in the OPAC templates, usually because there are template variable which need to be processed. Some of these variable, like system preferences, are a global setting which is common to many pages in the OPAC. I propose that these settings be defined in embedded JavaScript so that the scripts themselves can be moved to a separate file.

In my proposal, opac-bottom.inc will contain a section like this:

<script type="text/javascript">
    if (typeof KOHA == "undefined" || !KOHA) {
        var KOHA = {};
    }
    KOHA.paths = {
        "interface_theme":"[% interface %]/[% theme %]"
    }
    KOHA.preferences = {
        "BakerTaylorEnabled" : [% IF ( Koha.Preference( 'BakerTaylorEnabled' ) == 1 ) %]1[% ELSE %]0[% END %],

...and then an separate JS file will use those variables to conditionally load resources:

if( KOHA.preferences.Coce && KOHA.preferences.CoceProviders ){
    KOHA.externalResources.push( KOHA.paths.interface_theme + "/js/coce.js" );
    var NO_COCE_JACKET = _("No cover image available");
}

if( KOHA.externalResources.length > 0 ){
    Modernizr.load({
        load: KOHA.externalResources
    });
}

I'd appreciate comments anyone might have on this system. My goal, if this works well, is to then add a JavaScript concatenation/minification task for OPAC js assets. Moving as much JS as possible out of the templates will help us take advantage of that minification.