js根据字节自动转化KB或MB或GB

getFileSize(limit) { // 字节
      // bytes -->  KB  --> MB  -->GB
      var size = "";
      if(limit < 0.1 * 1024){                            //小于0.1KB，则转化成B
        size = limit.toFixed(2) + "B"
      }else if(limit < 0.1 * 1024 * 1024){            //小于0.1MB，则转化成KB
        size = (limit/1024).toFixed(2) + "KB"
      }else if(limit < 0.1 * 1024 * 1024 * 1024){        //小于0.1GB，则转化成MB
        size = (limit/(1024 * 1024)).toFixed(2) + "MB"
      }else{                                            //其他转化成GB
        size = (limit/(1024 * 1024 * 1024)).toFixed(2) + "GB"
      }
      var sizeStr = size + "";                        //转成字符串
      var index = sizeStr.indexOf(".");                    //获取小数点处的索引
      var dou = sizeStr.substr(index + 1 ,2)            //获取小数点后两位的值
      if(dou == "00"){                                //判断后两位是否为00，如果是则删除00
          return sizeStr.substring(0, index) + sizeStr.substr(index + 3, 2)
      }
      return size;
}