js格式化显示文件大小（bytes 转 KB、、、）

 //格式化文件大小
 function renderSize(value){
     if(null==value||value==''){
         return "0 Bytes";
     }
     var unitArr = new Array("Bytes","KB","MB","GB","TB","PB","EB","ZB","YB");
     var index=0;
     var srcsize = parseFloat(value);
     index=Math.floor(Math.log(srcsize)/Math.log(1024));
     var size =srcsize/Math.pow(1024,index);
     size=size.toFixed(2);//保留的小数位数
     return size+unitArr[index];
 }