jaredatch/Custom-Metaboxes-and-Fields-for-WordPress — comment on commit ebe7b54f30a0e492324252203d99e08f66baeaf1
File: jquery.cmbScripts.js line 51
By GaryJones:

As with PHP, use single quotes for strings in JS (though no performance benefit like PHP), so that double quotes can be used for HTML attribute values that might appear in strings.