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];
}