Wordpress/wp-admin/js/custom-background.min.js

(function(a){a(document).ready(function(){var b=a("#custom-background-image");a("#background-color").wpColorPicker({change:function(c,d){b.css("background-color",d.color.toString())},clear:function(){b.css("background-color","")}});a('input[name="background-position-x"]').change(function(){b.css("background-position",a(this).val()+" top")});a('input[name="background-repeat"]').change(function(){b.css("background-repeat",a(this).val())})})})(jQuery);