如何把任意大小的文件，按照其大小格式化为KB、MB、GB、TB等等

eg:
200 B ---> 200 B
1024B ---> 1 KB
10343532 B --> 9.86MB
1201759081 B --> 1.12GB
909584 B ---> 888.27 KB

function formatSize(size = 0) {
  let unit = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'X']
  let idx = 0
  let pre = size
  let cur = pre / 1024
  while (cur > 1) {
    pre = cur
    idx++
    cur /= 1024
  }
  pre = pre ? pre.toFixed(2) : 0
  return `${pre} ${unit[idx]}`
}