Pokemon evolution with Javascript streams

pokemon.js

'use strict';

const f = require('from');
const t = require('through');

const pokemons = f(['charmander', 'bulbasaur', 'squirtle']);

const evolve = t((pokemon) => {
  'use strict';
  let evolvedPokemon = pokemon;
  
  switch (pokemon) {
  case 'charmander':
    evolvedPokemon = 'charmeleon'; break;
  case 'bulbasaur':
    evolvedPokemon = 'ivysaur'; break;
  case 'squirtle':
    evolvedPokemon = 'wartortle'; break;
  }

  this.emit('data', evolvedPokemon);
});

const deploy = t((pokemon) => {
  console.log('Go', pokemon);
});

pokemons
  .pipe(evolve)
  .pipe(deploy);