The stream-transform package is a simple and powerful tool for transforming data in Node.js streams. It allows you to easily modify data as it passes through a stream, making it highly useful for tasks such as data manipulation, filtering, and aggregation in real-time data processing applications.

What are stream-transform's main functionalities?

Synchronous Transformation

This feature allows for synchronous data transformation within a stream. The provided code sample demonstrates how to read data from a CSV file, transform each record by joining its elements with a space, and then output the transformed data.

const transform = require('stream-transform');
const transformer = transform(function(record, callback){
  setTimeout(function(){
    callback(null, record.join(' ') + '\n');
  }, 500);
}, {parallel: 5});
require('fs').createReadStream('/path/to/source.csv').pipe(transformer).pipe(process.stdout);

Asynchronous Transformation

This feature supports asynchronous transformation of stream data. The code sample shows how to asynchronously convert each piece of data to uppercase before passing it through the stream.

const transform = require('stream-transform');
const transformer = transform(function(record, callback){
  process.nextTick(function(){
    callback(null, record.toUpperCase());
  });
});
require('fs').createReadStream('/path/to/source.txt').pipe(transformer).pipe(process.stdout);

Other packages similar to stream-transform

Readme

Source

Part of the CSV module, this project is a simple object transformation framework. It implements the Node.js stream.Transform API. It also provides a simple callback-based API for convenience. It is both extremely easy to use and powerful.

Documentation

Features

Extends the native Node.js transform stream API
Simplicity with the optional callback and sync API
Pipe transformations between readable and writable streams
Synchronous versus asynchronous user functions
Sequential and parallel execution
Accept object, array or JSON as input and output
Sequential or user-defined concurrent execution
Skip and multiply records
Alter or clone input records
MIT License

Usage

The module is built on the Node.js Stream API. For the sake of simplify, a simple callback API is also provided. To give you a quick look, here's an example of the callback API:

var transform = require('stream-transform');

input = [ [ '1', '2', '3', '4' ], [ 'a', 'b', 'c', 'd' ] ];
transform(input, function(data){
  data.push(data.shift());
  return data.join(',')+'\n';
}, function(err, output){
  output.should.eql([ '2,3,4,1\n', 'b,c,d,a\n' ]);
});

Development

Tests are executed with mocha. To install it, simple run npm install followed by npm test. It will install mocha and its dependencies in your project "node_modules" directory and run the test suite. The tests run against the CoffeeScript source files.

To generate the JavaScript files, run npm run coffee.

The test suite is run online with Travis. See the Travis definition file to view the tested Node.js version.

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Last updated on 03 Sep 2021

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