How do I write to a file in Node.js?

General Discussions
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1

I’m working with Node.js and need to write some content to a file, but I haven’t been able to get it working properly. I’ve looked through a few examples, but most seem outdated or unclear.

What’s the correct way to use built-in Node.js methods to write a file—whether it’s creating a new file or overwriting an existing one?

Also, is there a difference between using fs.writeFile() and fs.writeFileSync() for basic file operations? Would love a simple example to understand the right approach for a typical Node write file task.

2

Hey! I remember when I first started with Node.js, the easiest way I found to node write file was by using the asynchronous fs.writeFile() method from the built-in fs module. It’s simple and non-blocking, which is great because it won’t freeze your app while writing. Here’s a quick example:

const fs = require('fs');

fs.writeFile('output.txt', 'Hello, Node.js!', (err) => {
  if (err) throw err;
  console.log('File has been saved!');
});

This creates output.txt or overwrites it if it already exists. Since it’s async, you get a callback that handles errors or confirms success. I tend to use this method for most of my Node write file operations, especially when performance and not blocking the event loop are important!

3

Great point, @Rashmihasija ! I totally agree. If you’re looking for something a bit more straightforward, especially for scripts where timing isn’t a big issue, you might prefer the synchronous version: fs.writeFileSync(). It works exactly the same way as fs.writeFile(), but synchronously. So if you’re okay with waiting for the file write to complete before proceeding, it’s a good choice. Here’s an example:

const fs = require('fs');

try {
  fs.writeFileSync('output.txt', 'Sync write with Node.js');
  console.log('File written successfully!');
} catch (err) {
  console.error('Error writing file:', err);
}

I typically use fs.writeFileSync() when I’m writing simple CLI tools or scripts and need the write operation to complete before moving forward.

4

Exactly! And if you want even more control, say you’re dealing with appending or working with streamsfs.createWriteStream() is another great option. This method allows you to write to files chunk by chunk, which is really helpful for larger files. But, as you mentioned, whether you’re using fs.writeFile() or fs.writeFileSync(), the primary difference is async vs. sync behavior. If you’re focused on performance and scalability, go for async (fs.writeFile()). If simplicity and blocking behavior are more important, sync (fs.writeFileSync()) is your friend.

Here’s a quick async usage example for clarity:

const fs = require('fs');

const data = 'This is an example of writing files in Node.js asynchronously.';
fs.writeFile('example.txt', data, (err) => {
  if (err) console.error(err);
  else console.log('File written asynchronously!');
});

Both methods will create or overwrite files, so it really boils down to your use case and what fits best for your app’s needs. Just remember that if you don’t need the app to freeze while writing, async is often the way to go!