MIME Type Lookup Utility

0.0.2 · abandoned · verified Sun Apr 19

The `mime-lookup` library provides a focused utility for resolving MIME types based on file extensions. Unlike some alternatives, this package does not bundle its own MIME type database. Instead, it requires the user to supply a database, typically by integrating with the `mime-db` package. As of its only released version, 0.0.2, it offers core functionalities such as `lookup` for determining a MIME type from a given path, `extension` for retrieving a default file extension from a MIME type, and `define` for adding custom MIME type to extension mappings. It also includes `charsets.lookup` for charset mappings. Key differentiators include its lightweight nature due to the decoupled database, allowing for flexible custom database integration. First published in 2015 and last updated in 2016, the project appears to be unmaintained, making its release cadence non-existent.

Common errors

```
TypeError: Cannot read properties of undefined (reading 'extensions') (or similar for 'charsets' or 'types')
```
cause The `MimeLookup` instance was created without providing a database, or the provided database object does not have the expected structure.

fix Ensure you pass a valid MIME type database object, such as the one from `mime-db`, during instantiation: `const mime = new MimeLookup(require('mime-db'));`
```
Error: Cannot find module 'mime-db'
```
cause The `mime-db` package, which is commonly used to provide the MIME type database, has not been installed.

fix Install `mime-db` as a dependency: `npm install mime-db`.
```
Incorrect MIME type (e.g., 'application/octet-stream') returned for a known file extension.
```
cause The provided database is either missing the entry for the specific file extension, or the `lookup` method's input path is malformed, preventing proper extension extraction.

fix Verify that your database (e.g., `mime-db` version) contains the expected entry. Also, ensure the path passed to `mime.lookup()` is correctly formatted (e.g., `'file.ext'`, `'.ext'`). You can also `mime.define()` custom types if needed.

Warnings

breaking `mime-lookup` is an abandoned project, with its last commit in 2016 and no new releases since version 0.0.2. It is not actively maintained, which may lead to unaddressed bugs, security vulnerabilities, or compatibility issues with newer Node.js versions or ecosystems.
Fix: Consider using alternative, actively maintained MIME type libraries such as `mime-types` or `mime` (v2+).
gotcha The `mime-lookup` library is CommonJS-only, meaning it only supports `require()` for module imports. It does not provide ES module (ESM) support.
Fix: Ensure you are using CommonJS `require()` syntax for importing `mime-lookup` and any related packages like `mime-db`. For projects requiring ESM, a different library is necessary.
gotcha `mime-lookup` does not include a MIME type database internally. You *must* provide one during instantiation, typically by using the `mime-db` package.
Fix: Always initialize `MimeLookup` with a database, e.g., `new MimeLookup(require('mime-db'))`. Failure to do so will result in an instance that cannot resolve any MIME types.
gotcha The project's extremely low version number (0.0.2) from its initial release suggests it was either an early-stage project or intended to have a very minimal feature set. It may lack features, optimizations, or robust error handling found in more mature libraries.
Fix: Thoroughly test its functionality in your specific use case. For complex or mission-critical applications, consider a more mature and actively maintained alternative.

Install

npm install mime-lookup npm
yarn add mime-lookup yarn
pnpm add mime-lookup pnpm

Imports

MimeLookup
wrong:
```
import { MimeLookup } from 'mime-lookup';
```
correct:
```
const MimeLookup = require('mime-lookup');
```
This library is CommonJS-only and does not support ES module imports.
mimeDb (for database)
wrong:
```
import mimeDb from 'mime-db';
```
correct:
```
const mimeDb = require('mime-db');
```
The `mime-db` package, commonly used as the database for `MimeLookup`, is also CommonJS-only.
MimeLookup (instance creation)
wrong:
```
const mime = new MimeLookup();
```
correct:
```
const mime = new MimeLookup(require('mime-db'));
```
An instance of `MimeLookup` *must* be initialized with a database object; it does not come with a default.

Quickstart

This quickstart demonstrates how to instantiate `MimeLookup` using `mime-db`, perform basic MIME type lookups, retrieve extensions, and define custom MIME type mappings.

const MimeLookup = require('mime-lookup');
const mimeDb = require('mime-db'); // This is the recommended database

// Initialize MimeLookup with the mime-db database
const mime = new MimeLookup(mimeDb);

console.log('--- MIME Type Lookups ---');
console.log('file.txt:', mime.lookup('file.txt'));
console.log('image.jpeg:', mime.lookup('image.jpeg'));
console.log('.html:', mime.lookup('.html'));
console.log('unknown.xyz (default):', mime.lookup('unknown.xyz'));

console.log('\n--- Extension Lookups ---');
console.log('text/html:', mime.extension('text/html'));
console.log('application/json:', mime.extension('application/json'));

console.log('\n--- Custom Mappings ---');
mime.define({
    'application/x-custom-format': ['xcf', 'customfmt'],
    'text/markdown': ['md', 'markdown']
});
console.log('document.xcf:', mime.lookup('document.xcf'));
console.log('report.md:', mime.lookup('report.md'));
console.log('application/x-custom-format (extension):', mime.extension('application/x-custom-format'));

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