Cómo utilizar streams y pipelines en Node.js

Node.js allows efficient operations with streams, a key tool for improving performance when handling large amounts of data. Knowing the types of streams available, such as read, write, duplex and transform, opens up multiple possibilities. A very practical utility is the pipeline operation, which allows you to connect several processes in a clear and controlled sequence.

What types of streams are there and how do they work?

Streams can be categorized into four main types:

• Read: To read information from a source.
• Write: To write information to a destination.
• Duplex: Combination that allows both reading and writing simultaneously.
• Transform: To modify data during transfer.

How to transform content using streams?

To convert text to uppercase using streams, a stream type called transform is used, specifically designed to modify the information as it flows.

const  { Transform, pipeline  }  = require('stream');const  fs  = require('fs');const toUpperCase  = new Transform({  transform(chunk, encoding, callback)  {    this.push(chunk.toString().toUpperCase());    callback();   }});pipeline(   fs.createReadStream('input.txt'),  toUpperCase,   fs.createWriteStream('output.txt'),  (err)  =>  {    if (err) console.error('Error:', err);   });

In this operation:

• A file (input.txt) is read.
• Its contents are converted to uppercase.
• The result is saved in another file (output.txt).
• Any possible errors are handled correctly.

How to read files line by line with Node.js?

The readline utility allows to process a file line by line asynchronously, making it easy to read in an organized way, especially useful with large files.

const  fs  = require('fs');const readline  = require('readline');async function readLines()  {  const fileStream  =  fs.createReadStream('content.txt');  const  rl  = readline.createInterface({    input: fileStream,    crlfDelay: Infinity   });  try  {    for await (const line of  rl)  {      console.log(line);     }   } catch (error)  {    console.error(error);   }}readLines();

This method allows:

• Iterate over individual lines in the file.
• Perform specific actions on each line read, shown here in the console.

What are async iterables and how do they work?

Async iterables and for await simplify the handling of asynchronous operations, maintaining order in the results by creating linear and clear processes. In practice, this allows you to easily process streams in Node.js, preserving the structure and sequence of the content.

Go ahead and practice combining these methods! You can perform an operation that reads lines from a file, transforms them to uppercase and display or save them. Share how you solved the exercise in the comments.