How To Use __dirname in Node.js

To complete this tutorial, you will need:

• A general knowledge of Node.js. To learn more about Node.js, check out our How To Code in Node.js series.

This tutorial was verified with Node.js v17.2.0 and npm v8.2.0.

This tutorial will use the following sample directory structure to explore how __dirname works:

dirname-example
  ├──index.js
  ├──public
  ├──src
  │  ├──helpers.js
  │  └──api
  │      └──controller.js
  ├──cronjobs
  │  └──hello.js
  └──package.json

You can start by creating a dirname-example directory in your terminal:

mkdir dirname-example

Navigate to the project directory:

cd dirname-example

Initialize it as a Node.js project:

npm init --yes

Now, you will create the directories and files to experiment with.

You can use __dirname to check on which directories your files live.

Create and edit controller.js in the api subdirectory in the src directory:

console.log(__dirname)      // "/Users/Sam/dirname-example/src/api"
console.log(process.cwd())  // "/Users/Sam/dirname-example"

Then, run the script:

node src/api/controller.js

Create and edit hello.js in the cronjobs directory:

console.log(__dirname)     // "/Users/Sam/dirname-example/cronjobs"
console.log(process.cwd()) // "/Users/Sam/dirname-example"

Then, run the script:

node cronjobs/hello.js

Notice that __dirname has a different value depending on which file you console it out. The process.cwd() method also returns a value, but the project directory instead. The __dirname variable always returns the absolute path of where your files live.

In this section, you will explore how to use __dirname to make new directories, point to them, as well as add new files.

Making New Directories

To create a new directory in your index.js file, insert __dirname as the first argument to path.join() and the name of the new directory as the second:

const fs = require('fs');
const path = require('path');
const dirPath = path.join(__dirname, '/pictures');

fs.mkdirSync(dirPath);

Now you’ve created a new directory, pictures, after calling on the mdirSync() method, which contains __dirname as the absolute path.

Pointing to Directories

Another unique feature is its ability to point to directories. In your index.js file, declare a variable and pass in the value of __dirname as the first argument in path.join(), and your directory containing static files as the second:

express.static(path.join(__dirname, '/public'));

Here, you’re telling Node.js to use __dirname to point to the public directory that contains static files.

Adding Files to a Directory

You may also add files to an existing directory. In your index.js file, declare a variable and include __dirname as the first argument and the file you want to add as the second:

const fs = require('fs');
const path = require('path');
const filePath = path.join(__dirname, '/pictures');

fs.openSync(filePath, 'hello.jpeg');

Using the openSync() method will add the file if it does not exist within your directory.

Node.js provides a way for you to make and point to directories. And add files to existing directories with a modular environment variable.

For further reading, check out the Node.js documentation for __dirname, and the tutorial on using __dirname in the Express.js framework.