display-featured-image-genesis/includes/js/widget-selector.js

function term_postback ( select_id, taxonomy ) {
	'use strict';
	var data = {
		action: 'widget_selector',
		taxonomy: taxonomy
	};
	jQuery.post( displayfeaturedimagegenesis_ajax_object.ajax_url, data, function ( response ) {
		// Decode the data received.
		var list = jQuery.parseJSON( response );

		// Keep track of what was previously selected
		var control = jQuery( '#' + select_id );
		var old_value = control.val();

		// Clear out the old options, build up the new
		control.empty();
		jQuery.each( list, function ( key, value ) {
			var new_option = jQuery( '<option />' )
				.val( key ).text( value );
			control.val( '' );
			if ( value === old_value ) {
				control.val( old_value );
			}
			var method = !key ? 'prepend' : 'append';
			control[ method ]( new_option );
		} );
	} );
}