How To Write To A File In Javascript

In this blog post, we’ll explore how to write to a file using JavaScript. With the advent of Node.js, JavaScript has made its way to the server-side, allowing us to read and write files using the built-in fs module. However, writing and reading files is not possible in client-side JavaScript running in the browser due to security limitations.

Let’s dive into how to write to a file in JavaScript using the fs module in a Node.js environment.

1. Setup a Node.js Project

Before we begin, make sure you have Node.js installed in your system. Then, create a new folder for your project and navigate to it using the command prompt or terminal.

Initialize your project by running the following command:

npm init -y

This will create a package.json file in your project directory.

2. Writing to a File using the fs module

Create a new file called writeFile.js in your project directory. We’ll use the fs module’s writeFile function to write to a file.

const fs = require('fs');

const data = &quot;Hello, World! This is a &lt;a href=&quot;;&gt;<a href="">text file</a>&lt;/a&gt;.&quot;;

fs.writeFile(&#039;output.txt&#039;, data, (err) =&amp;gt; {
    if (err) {
        console.error(&#039;Error writing to file:&#039;, err);
    } else {
        console.log(&#039;File written successfully!&#039;);

In this example, we first import the fs module. Then, we create a string called data that we want to write to a file. We use the fs.writeFile function to create a new file called output.txt and write the contents of the data string to the file. The writeFile() function takes three arguments: the file name, the data to be written, and a callback function to handle errors and/or success messages.

3. Running the Script

To run the script, open your terminal or command prompt, navigate to your project directory, and execute the following command:

node writeFile.js

If the script executes successfully, you should see the following output:

File written successfully!

Additionally, you should now see a new file named output.txt in your project folder containing the text from the data string.


In this blog post, we’ve demonstrated how to write to a file in JavaScript using the fs module in a Node.js environment. Note that this method is not applicable to client-side JavaScript running in a web browser due to security restrictions. However, if you’re working with server-side JavaScript, the fs module offers a powerful and straightforward way to interact with the file system.