Reduced Advanced Reducer Example from funfunfunction.md

Original was from Reduce Advanced of funfunfunction. It was a great example, but I thought it could use a bit more of the ES6 goodness like template literals, destructuring, and the spread operators.

Also the reduced form is a more "pure" functional implementation since it doesn't mutate the original object with evil functions like push, but instead returns new data every time. A JS Bin is available to run and play with the modified version.

data.txt

mark johansson	waffle iron	80	2
mark johansson	blender	200	1
mark johansson	knife	10	4
Nikita Smith	waffle iron	80	1
Nikita Smith	knife	10	2
Nikita Smith	pot	20	3

reduce-advanced-original.js

import fs from 'fs'

var output = fs.readFileSync('data.txt', 'utf8')
  .trim()
  .split('\n')
  .map(line => line.split('\t'))
  .reduce((customers, line) => {
    customers[line[0]] = customers[line[0]] || []
    customers[line[0]].push({
      name: line[1],
      price: line[2],
      quantity: line[3],
    })
    return customers
  }, {})

console.log(JSON.stringify(output, null, 2))

reduce-advanced-reduced.js

const input = `mark johansson,waffle iron,80,2
mark johansson,blender,200,1
mark johansson,knife,10,4
Nikita Smith,waffle iron,80,1
Nikita Smith,knife,10,2
Nikita Smith,pot,20,3`;

const output = input
  .split('\n')
  .map(line => line.split(','))
  .reduce((customers, [customerName, name, price, quantity]) => ({
    ...customers, [customerName]: [...customers[customerName] || [],
      { name, price, quantity }]
    }),
  {});

console.log(output);