var imgUrl = 'a.jpg';
var positions = ['0 -184','0 -276','0 -368','0 -460'  ];
var ele=document.getElementById("boy");

animation(ele,positions,imgUrl);
function animation(ele,positions,imgUrl){
   ele.style.backgroundImage='url('+imgUrl+')';
   ele.style.backgroundRepeat='no-repeat';
   var index = 0;

   function run (){
      var positions=positions[index].split('');
       ele.style.backgroundPosition=positions[0]+'px'+positions[1]+'px';
       index++;
       if(index>=positions.length){
           index=0;
       }
       setTimeout(run,80);
   }
   run();
}