js将数字转换成文件大小

function size(num: number) {
  return (
    (
      [
        ["GB", Math.pow(1024, 3)],
        ["MB", Math.pow(1024, 2)],
        ["KB", Math.pow(1024, 1)],
        ["B", 1],
      ] as [string, number][]
    )
      .map((i) => [i[0], Math.floor(num / i[1])])
      .find((i) => i[1] > 0)
      // @ts-ignore
      ?.reduce((pre, cur) => cur + pre)
  );
}