Work with file paths in Node.js

  • 4 minutes

Node.js has a built-in mechanism for working with file system paths.

In the previous exercise, we didn't have many folders to find and look through. If you have many files or folders, manually building paths can get tedious. Node.js provides some built-in constants and utilities to make file paths easier.

Here, you'll learn about the Node.js path module and the __dirname constant so that you can make the program smarter and more resilient.

Determine the current directory

Sometimes, you don't know the directory where your program will run. You need it to just use the path of the current directory. Node.js exposes the full path to the current directory via the constant __dirname.

console.log(__dirname);

If you run that code from the sales folder in the following folder structure, the _dirname value will be /stores/201/sales.

📂 stores
    📂 201
        📂 sales

Work with paths

Paths are a subject that comes up so frequently that Node.js includes a module called path specifically for working with paths.

Just like the fs module, the path module ships with Node.js and doesn't need to be installed. You just need to reference it at the top of your file.

const path = require("path");

Join paths

The path module works with the concept of file and folder paths, which are just strings. For instance, if you want to get the path to the stores/201 folder, you can use the path module to do that.

console.log(path.join("stores", "201")); // stores/201

The reason why you would use the path module instead of concatenating strings is that your program might run on Windows or Linux. The path module will always format paths correctly for whatever operating system it's running on. In the preceding example, path.join would return stores\201 on Windows, with a backslash instead of a slash.

Determine filename extensions

The path module can also identify the extension of a filename. If you have a file and you want to identify if it's a JSON file, you can use the path.extname method.

console.log(path.extname("sales.json"));

Tip

The path module doesn't care whether or not things actually exist. Paths are conceptual, not physical. It's just building and parsing strings for you.

Get everything you need to know about a file or path

The path module contains many different methods that do various things. However, you can get most of the information that you need about a path or file by using the parse method. This method returns an object that contains the current directory you're in, the name of the file, the filename extension, and even the name of the file without the extension.

console.log(path.parse("stores/201/sales.json"));
// { root: '', dir: 'stores/201', base: 'sales.json', ext: '.json', name: 'sales' }

There are many more useful utility methods on the path module, but these are the core concepts that you'll likely use most often. In the next exercise, you'll use the path module to compose paths and identify .json files.