To make it easy to visualize, below is the following Record lookup table.

I just can't seem to find anywhere online where it tells you which of these are supposed to also contain charset=utf-8.

Should I just assume it's anything similar to text?

Take a look:

const MEDIA_TYPES: Record<string, string> = {
  ".md": "text/markdown",
  ".html": "text/html",
  ".htm": "text/html",
  ".json": "application/json",
  ".map": "application/json",
  ".txt": "text/plain",
  ".ts": "text/typescript",
  ".tsx": "text/tsx",
  ".js": "application/javascript",
  ".jsx": "text/jsx",
  ".gz": "application/gzip",
  ".css": "text/css",
  ".wasm": "application/wasm",
  ".mjs": "application/javascript",
  ".otf": "font/otf",
  ".ttf": "font/ttf",
  ".woff": "font/woff",
  ".woff2": "font/woff2",
  ".conf": "text/plain",
  ".list": "text/plain",
  ".log": "text/plain",
  ".ini": "text/plain",
  ".vtt": "text/vtt",
  ".yaml": "text/yaml",
  ".yml": "text/yaml",
  ".mid": "audio/midi",
  ".midi": "audio/midi",
  ".mp3": "audio/mp3",
  ".mp4a": "audio/mp4",
  ".m4a": "audio/mp4",
  ".ogg": "audio/ogg",
  ".spx": "audio/ogg",
  ".opus": "audio/ogg",
  ".wav": "audio/wav",
  ".webm": "audio/webm",
  ".aac": "audio/x-aac",
  ".flac": "audio/x-flac",
  ".mp4": "video/mp4",
  ".mp4v": "video/mp4",
  ".mkv": "video/x-matroska",
  ".mov": "video/quicktime",
  ".svg": "image/svg+xml",
  ".avif": "image/avif",
  ".bmp": "image/bmp",
  ".gif": "image/gif",
  ".heic": "image/heic",
  ".heif": "image/heif",
  ".jpeg": "image/jpeg",
  ".jpg": "image/jpeg",
  ".png": "image/png",
  ".tiff": "image/tiff",
  ".psd": "image/vnd.adobe.photoshop",
  ".ico": "image/vnd.microsoft.icon",
  ".webp": "image/webp",
  ".es": "application/ecmascript",
  ".epub": "application/epub+zip",
  ".jar": "application/java-archive",
  ".war": "application/java-archive",
  ".webmanifest": "application/manifest+json",
  ".doc": "application/msword",
  ".dot": "application/msword",
  ".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
  ".dotx": "application/vnd.openxmlformats-officedocument.wordprocessingml.template",
  ".cjs": "application/node",
  ".bin": "application/octet-stream",
  ".pkg": "application/octet-stream",
  ".dump": "application/octet-stream",
  ".exe": "application/octet-stream",
  ".deploy": "application/octet-stream",
  ".img": "application/octet-stream",
  ".msi": "application/octet-stream",
  ".pdf": "application/pdf",
  ".pgp": "application/pgp-encrypted",
  ".asc": "application/pgp-signature",
  ".sig": "application/pgp-signature",
  ".ai": "application/postscript",
  ".eps": "application/postscript",
  ".ps": "application/postscript",
  ".rdf": "application/rdf+xml",
  ".rss": "application/rss+xml",
  ".rtf": "application/rtf",
  ".apk": "application/vnd.android.package-archive",
  ".key": "application/vnd.apple.keynote",
  ".numbers": "application/vnd.apple.keynote",
  ".pages": "application/vnd.apple.pages",
  ".geo": "application/vnd.dynageo",
  ".gdoc": "application/vnd.google-apps.document",
  ".gslides": "application/vnd.google-apps.presentation",
  ".gsheet": "application/vnd.google-apps.spreadsheet",
  ".kml": "application/vnd.google-earth.kml+xml",
  ".mkz": "application/vnd.google-earth.kmz",
  ".icc": "application/vnd.iccprofile",
  ".icm": "application/vnd.iccprofile",
  ".xls": "application/vnd.ms-excel",
  ".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
  ".xlm": "application/vnd.ms-excel",
  ".ppt": "application/vnd.ms-powerpoint",
  ".pot": "application/vnd.ms-powerpoint",
  ".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
  ".potx": "application/vnd.openxmlformats-officedocument.presentationml.template",
  ".xps": "application/vnd.ms-xpsdocument",
  ".odc": "application/vnd.oasis.opendocument.chart",
  ".odb": "application/vnd.oasis.opendocument.database",
  ".odf": "application/vnd.oasis.opendocument.formula",
  ".odg": "application/vnd.oasis.opendocument.graphics",
  ".odp": "application/vnd.oasis.opendocument.presentation",
  ".ods": "application/vnd.oasis.opendocument.spreadsheet",
  ".odt": "application/vnd.oasis.opendocument.text",
  ".rar": "application/vnd.rar",
  ".unityweb": "application/vnd.unity",
  ".dmg": "application/x-apple-diskimage",
  ".bz": "application/x-bzip",
  ".crx": "application/x-chrome-extension",
  ".deb": "application/x-debian-package",
  ".php": "application/x-httpd-php",
  ".iso": "application/x-iso9660-image",
  ".sh": "application/x-sh",
  ".sql": "application/x-sql",
  ".srt": "application/x-subrip",
  ".xml": "application/xml",
  ".zip": "application/zip",
};

/** Returns the content-type based on the extension of a path. */
function contentType(pathname: string): string | undefined {
  return MEDIA_TYPES[pathname];
}

console.log(contentType("/dashboard/v1/index.html"));
console.log(contentType("/dashboard/v1/logo.svg"));

To make it easy to visualize, below is the following Record lookup table.

I just can't seem to find anywhere online where it tells you which of these are supposed to also contain charset=utf-8.

Should I just assume it's anything similar to text?

Take a look:

const MEDIA_TYPES: Record<string, string> = {
  ".md": "text/markdown",
  ".html": "text/html",
  ".htm": "text/html",
  ".json": "application/json",
  ".map": "application/json",
  ".txt": "text/plain",
  ".ts": "text/typescript",
  ".tsx": "text/tsx",
  ".js": "application/javascript",
  ".jsx": "text/jsx",
  ".gz": "application/gzip",
  ".css": "text/css",
  ".wasm": "application/wasm",
  ".mjs": "application/javascript",
  ".otf": "font/otf",
  ".ttf": "font/ttf",
  ".woff": "font/woff",
  ".woff2": "font/woff2",
  ".conf": "text/plain",
  ".list": "text/plain",
  ".log": "text/plain",
  ".ini": "text/plain",
  ".vtt": "text/vtt",
  ".yaml": "text/yaml",
  ".yml": "text/yaml",
  ".mid": "audio/midi",
  ".midi": "audio/midi",
  ".mp3": "audio/mp3",
  ".mp4a": "audio/mp4",
  ".m4a": "audio/mp4",
  ".ogg": "audio/ogg",
  ".spx": "audio/ogg",
  ".opus": "audio/ogg",
  ".wav": "audio/wav",
  ".webm": "audio/webm",
  ".aac": "audio/x-aac",
  ".flac": "audio/x-flac",
  ".mp4": "video/mp4",
  ".mp4v": "video/mp4",
  ".mkv": "video/x-matroska",
  ".mov": "video/quicktime",
  ".svg": "image/svg+xml",
  ".avif": "image/avif",
  ".bmp": "image/bmp",
  ".gif": "image/gif",
  ".heic": "image/heic",
  ".heif": "image/heif",
  ".jpeg": "image/jpeg",
  ".jpg": "image/jpeg",
  ".png": "image/png",
  ".tiff": "image/tiff",
  ".psd": "image/vnd.adobe.photoshop",
  ".ico": "image/vnd.microsoft.icon",
  ".webp": "image/webp",
  ".es": "application/ecmascript",
  ".epub": "application/epub+zip",
  ".jar": "application/java-archive",
  ".war": "application/java-archive",
  ".webmanifest": "application/manifest+json",
  ".doc": "application/msword",
  ".dot": "application/msword",
  ".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
  ".dotx": "application/vnd.openxmlformats-officedocument.wordprocessingml.template",
  ".cjs": "application/node",
  ".bin": "application/octet-stream",
  ".pkg": "application/octet-stream",
  ".dump": "application/octet-stream",
  ".exe": "application/octet-stream",
  ".deploy": "application/octet-stream",
  ".img": "application/octet-stream",
  ".msi": "application/octet-stream",
  ".pdf": "application/pdf",
  ".pgp": "application/pgp-encrypted",
  ".asc": "application/pgp-signature",
  ".sig": "application/pgp-signature",
  ".ai": "application/postscript",
  ".eps": "application/postscript",
  ".ps": "application/postscript",
  ".rdf": "application/rdf+xml",
  ".rss": "application/rss+xml",
  ".rtf": "application/rtf",
  ".apk": "application/vnd.android.package-archive",
  ".key": "application/vnd.apple.keynote",
  ".numbers": "application/vnd.apple.keynote",
  ".pages": "application/vnd.apple.pages",
  ".geo": "application/vnd.dynageo",
  ".gdoc": "application/vnd.google-apps.document",
  ".gslides": "application/vnd.google-apps.presentation",
  ".gsheet": "application/vnd.google-apps.spreadsheet",
  ".kml": "application/vnd.google-earth.kml+xml",
  ".mkz": "application/vnd.google-earth.kmz",
  ".icc": "application/vnd.iccprofile",
  ".icm": "application/vnd.iccprofile",
  ".xls": "application/vnd.ms-excel",
  ".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
  ".xlm": "application/vnd.ms-excel",
  ".ppt": "application/vnd.ms-powerpoint",
  ".pot": "application/vnd.ms-powerpoint",
  ".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
  ".potx": "application/vnd.openxmlformats-officedocument.presentationml.template",
  ".xps": "application/vnd.ms-xpsdocument",
  ".odc": "application/vnd.oasis.opendocument.chart",
  ".odb": "application/vnd.oasis.opendocument.database",
  ".odf": "application/vnd.oasis.opendocument.formula",
  ".odg": "application/vnd.oasis.opendocument.graphics",
  ".odp": "application/vnd.oasis.opendocument.presentation",
  ".ods": "application/vnd.oasis.opendocument.spreadsheet",
  ".odt": "application/vnd.oasis.opendocument.text",
  ".rar": "application/vnd.rar",
  ".unityweb": "application/vnd.unity",
  ".dmg": "application/x-apple-diskimage",
  ".bz": "application/x-bzip",
  ".crx": "application/x-chrome-extension",
  ".deb": "application/x-debian-package",
  ".php": "application/x-httpd-php",
  ".iso": "application/x-iso9660-image",
  ".sh": "application/x-sh",
  ".sql": "application/x-sql",
  ".srt": "application/x-subrip",
  ".xml": "application/xml",
  ".zip": "application/zip",
};

/** Returns the content-type based on the extension of a path. */
function contentType(pathname: string): string | undefined {
  return MEDIA_TYPES[pathname];
}

console.log(contentType("/dashboard/v1/index.html"));
console.log(contentType("/dashboard/v1/logo.svg"));

• javascript
• typescript
• mime-types
• deno

• 2 What do you mean by "are supposed to also contain charset=utf-8"? The charset (encoding) does not depend on, and cannot be derived from, the file extension. – Bergi Commented Jan 9, 2022 at 19:10
• I meant which "known file extensions" whose content type can usually be predicted provided someone isn't just mislabeling file extensions for the fun of it. – suchislife Commented Jan 9, 2022 at 19:16
• 2 No, I meant what I said: you cannot predict the charset from the file extension. A .html file should have html content (unless mislabelled), but you can't tell from the file extension whether that html content is encoded as UTF-8 or something else. – Bergi Commented Jan 9, 2022 at 19:19
• Ohhhhhhhhhhhhhh. I see your point. Perhaps determine it based on http header 'Content-Language': 'en-US',. Hmmm. Excellent point. – suchislife Commented Jan 9, 2022 at 19:20
• 1 So you read the files from disk and serve them via HTTP, and want to add the appropriate content-type header? Ok. Who stores the files on the disk, and what encoding do they use for text files? – Bergi Commented Jan 9, 2022 at 19:24

1 Answer 1

MDN Says:

For example, for any MIME type whose main type is text, you can add the optional charset parameter to specify the character set used for the characters in the data. If no charset is specified, the default is ASCII (US-ASCII) unless overridden by the user agent's settings. To specify a UTF-8 text file, the MIME type text/plain;charset=UTF-8 is used.

So, for anything based on text/... you can optionally add the charset.

https://developer.mozilla/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types#structure_of_a_mime_type

The following update to contentType() function demonstrates one solution.

/** Returns the content-type based on the extension of a path. */
function contentType(ext: string): string | undefined {

  const charsetUtf8 = "; charset=UTF-8";

  // Content types that do not start with text/.. but usually contain charset=utf-8
  const specialCase = [
    "application/json",
    "application/xml",
    "application/rss+xml",
  ];

  let outputContentType = MEDIA_TYPES[ext];

  // Return undefined.
  if(!outputContentType) return;

  if(outputContentType.startsWith("text/") || specialCase.includes(outputContentType)) {

    // Combine Content-Type with charset=utf-8
    outputContentType = outputContentType + charsetUtf8;

  // Return bined.
    return outputContentType;

  } else {
    // Return for any other types or undefined.
    return outputContentType;
  }
  
}

Then theoretically, you could return a 422: Unprocessable Entity on any content type NOT present in the mime type list.

let requestedFilePath = path.join("./", context.main.http.server.root, urlPathNameParsed.dir, urlPathNameParsed.base);

try {
  // try as file...
  const file = await Deno.readFile(requestedFilePath);

  // If file extension is not on media list...
  if(typeof(contentType(urlPathNameParsed.ext)) === 'undefined') { 

    // Set Content-Type header for this response
    responseHeaders.set('Content-Type', 'text/plain; charset=UTF-8');

    await e.respondWith(
      new Response("HTTP 422: Unprocessable Entity", {
        headers: responseHeaders,
        status: 422,
        statusText: 'Unprocessable Entity',
      })
    );

  } else {

    // Set Content-Type header for this response
    responseHeaders.set('Content-Type', `${contentType(urlPathNameParsed.ext)}`);

    // Build and send the response
    await e.respondWith(
      new Response(file, {
        headers: responseHeaders, 
        status: 200, 
        statusText: 'OK'
      })
    );

  }