https://jffsf.org/2019/wp-content/themes/voltage/js/jquery.backgroundPosition.js?ver=7.0.6

1/**
2 * @author Alexander Farkas
3 * v. 1.02
4 */
5(function($) {
6        $.extend($.fx.step,{
7            backgroundPosition: function(fx) {
8            if (fx.state === 0 && typeof fx.end == 'string') {
9                var start = $.curCSS(fx.elem,'backgroundPosition');
10                start = toArray(start);
11                fx.start = [start[0],start[2]];
12                var end = toArray(fx.end);
13                fx.end = [end[0],end[2]];
14                fx.unit = [end[1],end[3]];
15                        }
16            var nowPosX = [];
17            nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
18            nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];           
19            fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];
20            
21           function toArray(strg){
22               strg = strg.replace(/left|top/g,'0px');
23               strg = strg.replace(/right|bottom/g,'100%');
24               strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g,"$1px$2");
25               var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
26               return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
27           }
28        }
29        });
30})(jQuery);