If you wanna be fancy, you could declare a variable for `$('#customize-banner-form')` outside of the event handler. This would save jQuery from locating that element every time the change event fires.

Something like:

```
var $customize_banner_form = $('#customize-banner-form');

// When the variation selectbox changes, update the adjacent preview.
$(document).on('change', '#customize-banner-form select[name="variation"]', function(e) {
    var $select = $(this);
    var variationsText = $customize_banner_form.data('variationsText');
    var $preview = $('#text-preview');

    $preview.text(variationsText[$select.val()]);
});