How to convert data into uppercase using Tranform Stream with HTTP Server in NodeJS

index.js

const http = require('http');
const { Transform } = require('stream');

const server = http.createServer((req, res) => {
  // Create the transform stream:
  
  // OPTION #1
  const uppercase1 = new Transform({
    decodeStrings: false
  }); 
  
  uppercase1._transform = function (data, enc, cb) {
    cb(null, data.toString().toUpperCase());  
  };
  
  // OPTION #2
  const uppercase2 = new Transform({
    transform(chunk, encoding, callback) {
      this.push(chunk.toString().toUpperCase());
      callback();
    }
  });
  
  // OPTION #3
  const { StringDecoder } = require('string_decoder')

  class UppercaseCharacters extends Transform {
    constructor(options) {
      super (options)

      // The stream will have Buffer chunks. The
      // decoder converts these to String instances.
      this._decoder = new StringDecoder('utf-8')
    }

    _transform (chunk, encoding, callback) {
      // Convert the Buffer chunks to String.
      if (encoding === 'buffer') {
        chunk = this._decoder.write(chunk)
      }

      // Exit on CTRL + C.
      if (chunk === '\u0003') {
        process.exit()
      }

      // Uppercase lowercase letters.
      if (chunk >= 'a' && chunk <= 'z') {
        chunk = chunk.toUpperCase()
      }

      // Pass the chunk on.
      callback(null, chunk)
    }
  }
  const uppercase3 = new UppercaseCharacters()

  // OPTION #1
  req.pipe(uppercase1).pipe(res);

  // OPTION #2
  // req.pipe(uppercase2).pipe(res);

  // OPTION #3
  // req.pipe(uppercase3).pipe(res);
})