hono/deno_dist/utils/mime.ts

export const getMimeType = (filename: string): string | undefined => {
  const regexp = /\.([a-zA-Z0-9]+?)$/
  const match = filename.match(regexp)
  if (!match) {
    return
  }
  let mimeType = mimes[match[1]]
  if ((mimeType && mimeType.startsWith('text')) || mimeType === 'application/json') {
    mimeType += '; charset=utf-8'
  }
  return mimeType
}

const mimes: Record<string, string> = {
  aac: 'audio/aac',
  abw: 'application/x-abiword',
  arc: 'application/x-freearc',
  avi: 'video/x-msvideo',
  avif: 'image/avif',
  av1: 'video/av1',
  azw: 'application/vnd.amazon.ebook',
  bin: 'application/octet-stream',
  bmp: 'image/bmp',
  bz: 'application/x-bzip',
  bz2: 'application/x-bzip2',
  csh: 'application/x-csh',
  css: 'text/css',
  csv: 'text/csv',
  doc: 'application/msword',
  docx: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
  eot: 'application/vnd.ms-fontobject',
  epub: 'application/epub+zip',
  gif: 'image/gif',
  gz: 'application/gzip',
  htm: 'text/html',
  html: 'text/html',
  ico: 'image/x-icon',
  ics: 'text/calendar',
  jar: 'application/java-archive',
  jpeg: 'image/jpeg',
  jpg: 'image/jpeg',
  js: 'text/javascript',
  json: 'application/json',
  jsonld: 'application/ld+json',
  map: 'application/json',
  mid: 'audio/x-midi',
  midi: 'audio/x-midi',
  mjs: 'text/javascript',
  mp3: 'audio/mpeg',
  mp4: 'video/mp4',
  mpeg: 'video/mpeg',
  mpkg: 'application/vnd.apple.installer+xml',
  odp: 'application/vnd.oasis.opendocument.presentation',
  ods: 'application/vnd.oasis.opendocument.spreadsheet',
  odt: 'application/vnd.oasis.opendocument.text',
  oga: 'audio/ogg',
  ogv: 'video/ogg',
  ogx: 'application/ogg',
  opus: 'audio/opus',
  otf: 'font/otf',
  pdf: 'application/pdf',
  php: 'application/php',
  png: 'image/png',
  ppt: 'application/vnd.ms-powerpoint',
  pptx: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
  rtf: 'application/rtf',
  sh: 'application/x-sh',
  svg: 'image/svg+xml',
  swf: 'application/x-shockwave-flash',
  tar: 'application/x-tar',
  tif: 'image/tiff',
  tiff: 'image/tiff',
  ts: 'video/mp2t',
  ttf: 'font/ttf',
  txt: 'text/plain',
  vsd: 'application/vnd.visio',
  wasm: 'application/wasm',
  webm: 'video/webm',
  weba: 'audio/webm',
  webp: 'image/webp',
  woff: 'font/woff',
  woff2: 'font/woff2',
  xhtml: 'application/xhtml+xml',
  xls: 'application/vnd.ms-excel',
  xlsx: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
  xml: 'application/xml',
  xul: 'application/vnd.mozilla.xul+xml',
  zip: 'application/zip',
  '3gp': 'video/3gpp',
  '3g2': 'video/3gpp2',
  '7z': 'application/x-7z-compressed',
  gltf: 'model/gltf+json',
  glb: 'model/gltf-binary',
}