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"));

CodePudding user response：

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.org/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(pathname: 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 outputMediaType = MEDIA_TYPES[pathname];

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

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

  }

  return outputMediaType;
}