Introduction

__dirname is an environment variable that tells you the absolute path of the directory containing the currently executing file.

In this article, you will explore how to implement __dirname in your Node.js project.

Prerequisites

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.

Structuring Your Directories

This tutorial will use the following sample directory structure to explore how __dirname works. To begin your Node.js project, let’s organize your directories and files:

node-app
  ├──index.js
  ├──public
  ├──src
  │  ├──helpers.js
  │  └──api
  │      └──controller.js
  ├──cronjobs
  │  ├──pictures
  │  └──hello.js
  └──package.json

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

console.log(__dirname)      // "/Users/Sam/node-app/src/api"
console.log(process.cwd())  // "/Users/Sam/node-app"

console.log(__dirname)     // "/Users/Sam/node-app/cronjobs"
console.log(process.cwd()) // "/Users/Sam/node-app"

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.

Working With Directories

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

Conclusion

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.