How to Send File to Client in Node.js

In this article, we’ll learn about sending files to the client in Node.js using Express.

Use Express to Send File in Node.js

Express.js or Express is a back-end web utility framework for Node.js. Express is a Node.js web application framework that provides a robust characteristic set for web and mobile applications.

The function res.sendFile() passes the file in the specified path and sets the HTTP header field for the content-type response based on the filename extension.

Syntax:

res.sendFile(path[, options][, fn])

Follow the instructions below for sending the file to the client.

1. Install the Express package.

   $ npm install express
   

2. Create an index.js file and run the below command.

   node index.js
   

3. Create a helloworld.txt file.

   Hello World!
   

4. Run the index.js file by passing the code snippet below.

Complete Source Code - index.js:

const express = require('express');
const app = express();
const path = require('path');
const PORT = 3001;

app.get('/', (req, res, next) => {
  const fileName = 'helloworld.txt';
  res.sendFile(fileName, {root: path.join(__dirname)}, (err) => {
    if (err) {
      next(err);
    } else {
      console.log('File Sent:', fileName);
    }
  });
});

app.listen(PORT, (err) => {
  if (err) console.log(err);
  console.log('Server listening on PORT', PORT);
});

In the above example, we created a server that listens on the specified port 3001. Once the server listens to the specified port, it will execute the code inside the first matching route.

The response object will then be returned to the client with the sendFile() method. If any error is encountered, it will pass the error to the error handler using the next() method.

If everything is smooth, it will return the response object to the client with the file’s content.

Try to run the above code in replit, which supports Node.js, and it will display the below result.

Output:

Server listening on PORT 3001
File Sent: helloworld.txt

Run Code Demo