js file对象 文件大小转换可视容易阅读的单位

function returnFileSize(number) {
  if(number < 1024) {
    return number + 'bytes';
  } else if(number >= 1024 && number < 1048576) {
    return (number/1024).toFixed(1) + 'KB';
  } else if(number >= 1048576) {
    return (number/1048576).toFixed(1) + 'MB';
  }
}