Express req.range() Method

Posted in Express Tutorial

Updated on Feb 17, 2024

By Mari Selvan

👁️ 31 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

Handling range requests efficiently is crucial for optimizing the performance of web applications. Express.js provides a helpful method, req.range(), which simplifies the process of dealing with HTTP range requests.

In this guide, we'll delve into the syntax, functionality, and practical use cases of the req.range() method.

💡 Syntax

The req.range() method is used within a route handler to parse and extract the range information from the HTTP request headers. The syntax is as follows:

syntax.js

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const range = req.range(size, options);

size (optional): The total size of the resource being requested. It helps determine the length of the requested range.
options (optional): Additional options that can be provided, such as combine to merge overlapping ranges.

❓ How req.range() Works

The req.range() method simplifies the handling of Range requests specified by the Range HTTP header. It parses the header and returns an array of ranges, making it easier for developers to respond with the requested portion of a resource.

example.js

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app.get('/video', (req, res) => {
  const videoPath = 'path/to/video.mp4';
  const videoSize = fs.statSync(videoPath).size;

  // Parse the Range header
  const range = req.range(videoSize);

  // If no valid ranges are specified, or if the range is invalid, respond with 416 Range Not Satisfiable
  if (!range) {
    res.status(416).end();
    return;
  }

  // Respond with the requested range
  res.status(206).sendFile(videoPath, {
    start: range[0].start,
    end: range[0].end,
  });
});

In this example, the route handler for /video uses req.range() to parse the Range header and responds with the specified portion of the video file.

📚 Use Cases

Streaming Large Files:

Use req.range() to efficiently stream large files by responding with the specified range, facilitating smoother downloads.

example.js

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app.get('/large-file', (req, res) => {
  const filePath = 'path/to/large-file.zip';
  const fileSize = fs.statSync(filePath).size;

  // Parse the Range header
  const range = req.range(fileSize);

  // If no valid ranges are specified, or if the range is invalid, respond with 416 Range Not Satisfiable
  if (!range) {
    res.status(416).end();
    return;
  }

  // Respond with the requested range
  res.status(206).sendFile(filePath, {
    start: range[0].start,
    end: range[0].end,
  });
});

🏆 Best Practices

Check for Valid Ranges:

Always check the result of req.range() to ensure valid range requests. Respond with an appropriate status code (e.g., 416 Range Not Satisfiable) if the requested range is invalid.
example.js
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```
const range = req.range(size);

if (!range) {
  res.status(416).end();
  return;
}
```
Combine Overlapping Ranges:

Consider using the combine option when calling req.range() to merge overlapping ranges. This can simplify your logic when responding to multiple range requests.
example.js
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```
const range = req.range(size, { combine: true });
```

🎉 Conclusion

The req.range() method in Express.js provides a convenient way to handle Range requests, making it easier to implement efficient streaming of partial content. By understanding its syntax, functionality, and best practices, you can optimize your Express.js applications for better performance when serving partial content.

Now, armed with knowledge about the req.range() method, go ahead and enhance your Express.js projects for improved handling of range requests!