Introduction to merge-stream

The merge-stream module in Node.js is a powerful utility that allows developers to merge multiple streams into one, simplifying data management and enhancing performance. In this article, we will explore the various APIs provided by merge-stream and demonstrate their usage with code snippets and a practical application example.

Getting Started

To use merge-stream, you first need to install it via npm:

npm install merge-stream

Basic Usage

Merging two streams is straightforward with merge-stream. Here’s a simple example:

const merge = require('merge-stream');
const stream1 = getReadableStreamSomehow();
const stream2 = getReadableStreamSomehow();
const mergedStream = merge(stream1, stream2);

mergedStream.on('data', function(chunk) {
  console.log(chunk);
});

Adding Streams Dynamically

You can dynamically add streams to an already created merge stream:

const merge = require('merge-stream');
const stream1 = getReadableStreamSomehow();
const stream2 = getReadableStreamSomehow();
const mergedStream = merge(stream1);

mergedStream.add(stream2);

mergedStream.on('data', function(chunk) {
  console.log(chunk);
});

Error Handling

It’s important to handle errors in streams. Here’s an example:

const merge = require('merge-stream');
const stream1 = getReadableStreamWithError();
const stream2 = getReadableStreamSomehow();
const mergedStream = merge(stream1, stream2);

mergedStream.on('data', function(chunk) {
  console.log(chunk);
});

mergedStream.on('error', function(err) {
  console.error('Stream error:', err);
});

Practical Application Example

Let’s create a simple application that merges data from multiple APIs and processes it as a single stream:

const merge = require('merge-stream');
const axios = require('axios');
const { Readable } = require('stream');

async function fetchData(url) {
  const response = await axios.get(url);
  const stream = new Readable();
  stream.push(JSON.stringify(response.data));
  stream.push(null);
  return stream;
}

async function main() {
  const stream1 = await fetchData('https://api.example.com/data1');
  const stream2 = await fetchData('https://api.example.com/data2');

  const mergedStream = merge(stream1, stream2);

  mergedStream.on('data', function(chunk) {
    console.log('Received data:', chunk.toString());
  });

  mergedStream.on('end', function() {
    console.log('All data received.');
  });
}

main();

The above example demonstrates how to merge data retrieved from two different APIs and output them as a single stream, making data management much simpler and more efficient.

With its powerful stream merging capabilities, merge-stream is an essential tool for Node.js developers working with stream data.

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