Express res.sendFile() Method

Posted in Express Tutorial

Updated on Oct 28, 2024

By Mari Selvan

👁️ 212 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In web development, serving files is a common task, whether it's static assets, images, or entire HTML documents.

Express.js simplifies this process with the res.sendFile() method, designed to effortlessly send files as responses.

In this guide, we'll explore the syntax, use cases, and best practices of the res.sendFile() method in Express.js.

💡 Syntax

The syntax for the res.sendFile() method is straightforward:

syntax.js

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

path: A string representing the file path or a complete file path.
options (optional): An object with additional options for sending the file.
callback (optional): A callback function that will be executed once the file is sent.

❓ How res.sendFile() Works

The res.sendFile() method is used to send a file as an HTTP response to a client. It automatically sets the appropriate Content-Type header based on the file extension and provides options for additional configurations.

example.js

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const express = require('express');
const app = express();

app.get('/download/:file', (req, res) => {
  const fileName = req.params.file;
  const filePath = `./downloads/${fileName}`;
  
  res.sendFile(filePath, { root: __dirname });
});

const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}`);
});

In this example, a route is created to handle requests for downloading files. The res.sendFile() method is used to send the requested file from the 'downloads' directory.

📚 Use Cases

Serving Static Files:

Use res.sendFile() to serve static files like HTML, CSS, and JavaScript from a specified directory.

example.js

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app.use(express.static('public'));

app.get('/home', (req, res) => {
  res.sendFile('index.html', { root: __dirname + '/public' });
});

File Download Routes:

Create routes dedicated to file downloads, using res.sendFile() to send files in response to client requests.

example.js

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app.get('/download/:file', (req, res) => {
  const fileName = req.params.file;
  const filePath = `./downloads/${fileName}`;
  
  res.sendFile(filePath, { root: __dirname });
});

🏆 Best Practices

Security Considerations:

Ensure that file paths are properly sanitized and validated to prevent directory traversal attacks.

example.js

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app.get('/download/:file', (req, res) => {
  const fileName = req.params.file;
  
  // Validate file name to prevent directory traversal
  if (!isValidFileName(fileName)) {
    res.status(400).send('Invalid file name');
    return;
  }
  
  const filePath = `./downloads/${fileName}`;
  res.sendFile(filePath, { root: __dirname });
});

Setting Custom Headers:

Use the options parameter to set custom headers if needed, such as Content-Disposition for controlling file download behavior.

example.js

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app.get('/download/:file', (req, res) => {
  const fileName = req.params.file;
  const filePath = `./downloads/${fileName}`;
  
  const options = {
    headers: {
      'Content-Disposition': `attachment; filename=${fileName}`
    }
  };
  
  res.sendFile(filePath, options);
});

🎉 Conclusion

The res.sendFile() method in Express.js simplifies the process of serving files, making it an essential tool for handling various file-related scenarios. Whether you're serving static assets or providing file downloads, understanding how to use res.sendFile() will enhance your Express.js applications.

Now, equipped with knowledge about the res.sendFile() method, go ahead and streamline your file-serving tasks in Express.js!