JS 文件大小转换

// 1 G = 1073741824 B
// 1 MB = 1048576 B
// 1 KB = 1024 B
let fileSize = 1000 // File.size 得到文件大小，单位字节(B)
let result = ''
if (fileSize >= 1073741824) {
  // B => GB
  result = fileSize % 1073741824 === 0 ? fileSize / 1073741824 + 'G' : Math.trunc(fileSize / 1073741824) + 'G'
} else if (fileSize >= 1048576) {
  // B => MB
  result = fileSize % 1048576 === 0 ? fileSize / 1048576 + 'MB' :  Math.trunc(fileSize / 1048576) + 'MB'
} else if (fileSize >= 1024) {
  // B => KB
  result = fileSize % 1024 === 0 ? fileSize / 1024 + 'KB' :  Math.trunc(fileSize / 1024) + 'KB'
} else {
  result = fileSize + 'B'
}
console.log(result)