Introduction to Combined-Stream in Node.js

The combined-stream module in Node.js is a powerful tool for handling multiple data streams. It allows you to combine multiple readable streams into a single readable stream. This is particularly useful when you need to manage data from different sources or when you require advanced streaming capabilities.

Installing Combined-Stream

  npm install combined-stream

Basic Usage

Here’s how you can use the combined-stream module to combine multiple streams:

  
    const CombinedStream = require('combined-stream');
    const fs = require('fs');

    const combinedStream = CombinedStream.create();

    combinedStream.append(fs.createReadStream('file1.txt'));
    combinedStream.append(fs.createReadStream('file2.txt'));

    combinedStream.pipe(fs.createWriteStream('combined.txt'));
  

Appending Buffer

You can also append Buffers to the combined stream:

  
    combinedStream.append(Buffer.from('Hello, '));
    combinedStream.append(Buffer.from('world!'));
  

Promise Support

combined-stream also supports appending data from Promises:

  
    const fetch = require('node-fetch');

    combinedStream.append(() =>
      fetch('https://api.example.com/data')
        .then(res => res.body)
    );
  

Appending Streams Conditionally

Here is an example of appending streams conditionally:

  
    const shouldAppendFile2 = true;

    combinedStream.append(fs.createReadStream('file1.txt'));

      if (shouldAppendFile2) {
      combinedStream.append(fs.createReadStream('file2.txt'));
    }

    combinedStream.pipe(fs.createWriteStream('combined.txt'));
  

Error Handling

Handling errors with combined-stream is straightforward:

  
    combinedStream.on('error', (err) => {
      console.error('An error occurred:', err);
    });

    combinedStream.pipe(fs.createWriteStream('combined.txt'));
  

Real-World Example: Combining Log Files

In this example, we’ll combine multiple log files into a single log file:

  
    const CombinedStream = require('combined-stream');
    const fs = require('fs');

    const logFiles = ['log1.txt', 'log2.txt', 'log3.txt'];
    const combinedLogStream = CombinedStream.create();

    logFiles.forEach((file) => {
      combinedLogStream.append(fs.createReadStream(file));
    });

    combinedLogStream.pipe(fs.createWriteStream('combined.log'));

    console.log('Log files combined successfully!');
  

Conclusion

The combined-stream module is a versatile and powerful tool for managing multiple data streams in Node.js. Whether you’re working with files, buffers, or promises, combined-stream can help you streamline your data handling processes.

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