How to Get a File Extension in Node.js

Tari Ibaba
Last updated on September 29, 2022
How to Get a File Extension in Node.js

To get the extension of a file in Node.js, we can use the extname() method from the path module.

For example:

const path = require('path');

path.extname('style.css') // .css

path.extname('image.png') // .png

path.extname('prettier.config.js') // .js

11 Amazing New Features in ES13

11 Amazing New Features in ES13
Get up to speed with all the latest features added in ECMAScript 13 to modernize your JavaScript with shorter and more expressive code.

The extname() method

The extname() method returns the extension of the given path from the last occurrence of the . (period) character to the end of the string in the last part of the path.

If there is no . in the last part of the path, or if the path starts with . and it is the only . character in the path, extname() returns an empty string.

path.extname('index.'); // .

path.extname('index'); // '' (empty string)

path.extname('.index');   // '' (empty string)

path.extname('.index.html'); // .html

If the path is not a string, extname() throws a TypeError.

const path = require('path');

// ❌ TypeError: Received type number instead of string
path.extname(123);

// ❌ TypeError: Received type boolean instead of string
path.extname(false);

// ❌ TypeError: Received URL instance instead of string
path.extname(new URL('https://example.com/file.txt'));

// ✅ Received type of string
path.extname('package.json'); // .json

See also