Node.js — Get a File‘s Extension

In some situations, you may need to retrieve the extension of a file on your local disk. Node.js comes with built-in functionality that you can use in your application.

This tutorial shows you how to retrieve the file extension in Node.js.

Node.js Series Overview

  1. String Replace All Appearances
  2. Remove All Whitespace From a String in JavaScript
  3. Generate a Random ID or String in Node.js or JavaScript
  4. Remove Extra Spaces From a String in JavaScript or Node.js
  5. Remove Numbers From a String in JavaScript or Node.js
  6. Get the Part Before a Character in a String in JavaScript or Node.js
  7. Get the Part After a Character in a String in JavaScript or Node.js
  8. How to Check if a Value is a String in JavaScript or Node.js
  9. Check If a String Includes All Strings in JavaScript/Node.js/TypeScript
  10. Check if a Value is a String in JavaScript and Node.js
  11. Limit and Truncate a String to a Given Length in JavaScript and Node.js
  12. Split a String into a List of Characters in JavaScript and Node.js
  13. How to Generage a UUID in Node.js
  14. Reverse a String in JavaScript or Node.js
  15. Split a String into a List of Lines in JavaScript or Node.js
  16. Split a String into a List of Words in JavaScript or Node.js
  17. Detect if a String is in camelCase Format in Javascript or Node.js
  18. Check If a String Is in Lowercase in JavaScript or Node.js
  19. Check If a String is in Uppercase in JavaScript or Node.js
  20. Get the Part After First Occurrence in a String in JavaScript or Node.js
  21. Get the Part Before First Occurrence in a String in JavaScript or Node.js
  22. Get the Part Before Last Occurrence in a String in JavaScript or Node.js
  23. Get the Part After Last Occurrence in a String in JavaScript or Node.js
  24. How to Count Words in a File
  25. How to Shuffle the Characters of a String in JavaScript or Node.js
  26. Append Characters or Words to a String in JavaScript or Node.js (Coming soon)
  27. Check if a String is Empty in JavaScript or Node.js (Coming soon)
  28. Ensure a String Ends with a Given Character in JavaScript or Node.js (Coming soon)
  29. Left-Trim Characters Off a String in JavaScript or Node.js (Coming soon)
  30. Right-Trim Characters Off a String in JavaScript or Node.js (Coming soon)
  31. Lowercase the First Character of a String in JavaScript or Node.js (Coming soon)
  32. Uppercase the First Character of a String in JavaScript or Node.js (Coming soon)
  33. Prepend Characters or Words to a String in JavaScript or Node.js (Coming soon)

Retrieve the File Extension

Node.js’ integrated path module provides a Path.extname method. This method accepts a file path as a string. You can either use the Path.extname(path) method directly in your code or create yourself a utility function.

Here’s a sample utility method returning a file’s extension:

import Path from 'path'

/**
 * Returns the current operating system release version.
 *
 * @param {String} filePath
 *
 * @returns {String}
 */
function fileExtension (filePath) {  
  return Path.extname(filePath)
}

You may then use the fileExtension utility method like this:

fileExtension('tutorial.md')  
// '.md'

fileExtension('fs.tutorial.md')  
// '.md'

fileExtension('tutorial.')  
// '.'

fileExtension('tutorial')  
// ''

fileExtension('.md')  
// ''

fileExtension('.tutorial.md')  
// '.md'

Use the @supercharge/fs Package

I’m the maintainer of the @supercharge/fs package providing convenient file system utilities. The @supercharge/fs package comes with a handy Fs.extension(path) method returning the file extension of the given path (including the dot):

import Fs from '@supercharge/fs'

Fs.extension('tutorial.md')  
// '.md'

Fs.extension('fs.tutorial.md')  
// '.md'

Fs.extension('tutorial.')  
// '.'

Fs.extension('tutorial')  
// ''

Fs.extension('.md')  
// ''

Fs.extension('.tutorial.md')  
// '.md'

That’s it!


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