A way to write JS encapsulation motion framework

function animate(obj, json, interval, sp, fn) {
  clearInterval(obj.timer);
  //var k = 0;
  //var j = 0;
  function getStyle(obj, arr) {
    if(obj.currentStyle){
      return obj.currentStyle[arr];  //针对ie
    } else {
      return document.defaultView.getComputedStyle(obj, null)[arr]; 
    }
  }
  obj.timer = setInterval(function(){
    //j ++;
    var flag = true;
    for(var arr in json) {
      var icur = 0;
      //k++;
      if(arr == "opacity") {
        icur = Math.round(parseFloat(getStyle(obj, arr))*100);
      } else {
        icur = parseInt(getStyle(obj, arr));
      }
      var speed = (json[arr] - icur) * sp;
      speed = speed > 0 ? Math.ceil(speed): Math.floor(speed);
      if(icur != json[arr]){
        flag = false;
      } 
      if(arr == "opacity"){
        obj.style.filter = "alpha(opacity : '+(icur + speed)+' )";
        obj.style.opacity = (icur + speed)/100;
      }else {
        obj.style[arr] = icur + speed + "px";
      }
      //console.log(j + "," + arr +":"+ flag);
    }
    if(flag){
      clearInterval(obj.timer);
      //console.log(j + ":" + flag); 
      //console.log("k = " + k);
      //console.log("j = " + j);
      //console.log("DONE");
      if(fn){
        fn();
      }
    }
  },interval);
}