why-pipe-is-awesome.js

console.clear()

const R = require('ramda')

const cart = [
  { name: 'apples', price: 2.49 },
  { name: 'soap', price: 1.99 },
  { name: 'milk', price: 2.99 },
  { name: 'eggs', price: 3.99 },
  { name: 'carrots', price: 2.99 },
  { name: 'butter', price: 1.49 },
  { name: 'fish', price: 9 },
  { name: 'lettuce', price: 2.99 },
  { name: 'broccoli', price: 4.99 },
  { name: 'lemons', price: 3.49 }
]

const toUSD = (amount) => amount.toLocaleString('en-US', {
  style: 'currency',
  currency: 'USD',
})

// Pure functional approach
const getTotalPrice_FP = (cart) => R.pipe( //https://ramdajs.com/docs/#pipe
  R.pluck('price'), // https://ramdajs.com/docs/#pluck
  R.reduce(R.add, 0), // https://ramdajs.com/docs/#reduce
  toUSD,
)(cart)

// Idiomatic JS apprpach. Harder to read but still not too bad.
const getTotalPrice_IDOMATIC_JS = (cart) => toUSD(cart
  .map(p => p.price)
  .reduce((prev, curr) => prev + curr, 0))

// Imperative approach. Yuckkers harder.
const getTotalPrice_IMPL = (cart) => {
  let price = 0
  for (let i = 0; i < cart.length; i++) {
    price += cart[i].price
  }

  return toUSD(price)
}

console.log(getTotalPrice_FP(cart))
console.log(getTotalPrice_IDOMATIC_JS(cart))
console.log(getTotalPrice_IMPL(cart))