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  3. Node.js — Get a File‘s Extension

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

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  3. How to Create an Empty File
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  6. Check If a Path Is a Directory
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  10. Read File Content as String
  11. Check If a Directory Is Empty
  12. How to Create a Directory (and Parents If Needed)
  13. Get a File‘s Extension
  14. Get the Size of a File
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  16. Read a JSON File
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  23. What is `Fs.realpath`?
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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!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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