async-iterators.js

/***************************************************
 * Getúlio Magela Silva (gm50x)
 * 
 * Running Instructions:
 * node async-iterators {for-each|for-of|map}
 * 
 * Reference Material (NOT MINE):
 * https://zellwk.com/blog/async-await-in-loops/
 ***************************************************/


const getRandomInt = (max = 1) => Math.floor(Math.random() * Math.floor(max))
const getRandomIntAsync = max => new Promise(resolve => setTimeout(() => resolve(getRandomInt(max)), 1000))

const _map = () => new Promise(async (resolve) =>{
  console.log('-----ASYNC MAP-----')
  const fruits = [
    { name: 'Apple', price: 1 },
    { name: 'Banana', price: 1 },
    { name: 'Grapes', price: 1 }
  ]

  const items = fruits.map(i => ({...i}))
  const raisedItems = await Promise.all(items.map(async item => {
    const raise = 1 + await getRandomIntAsync(10)
    return {...item, price: item.price * raise}
  }))
  console.log('items mapped after a raise', raisedItems)
  console.log('-----ASYNC MAP DONE-----')

  resolve();
})

const _forEach = () => new Promise(async (resolve) => {
  console.log('-----ASYNC FOR-----')

  const fruits = [
    { name: 'Apple', price: 1 },
    { name: 'Banana', price: 1 },
    { name: 'Grapes', price: 1 }
  ]
  const items = fruits.map(i => ({...i}))

  items.forEach(async item => {
    const raise = 1 + await getRandomIntAsync(10)
    item.price *= raise
    console.log('item price in loop', item)
  })

  console.log('original items after forEach', items)
  console.log('-----ASYNC FOR DONE-----')
  resolve()
})

const _forOf = () => new Promise(async (resolve) => {
  console.log('-----ASYNC FOR..OF-----')
  const fruits = [
    { name: 'Apple', price: 1 },
    { name: 'Banana', price: 1 },
    { name: 'Grapes', price: 1 }
  ]
  const items = fruits.map(i => ({...i}))

  console.log('propper loop manipulation')
  for (const item of items) {
    const raise = 1 + await getRandomIntAsync(10)
    item.price *= raise
  }
  console.log('after loop manipulation', items)
  console.log('-----ASYNC FOR..OF DONE-----')
  resolve()
})

const main = async ([n, entrypoint, selectedOption]) => {
  const options = {'for-each': _forEach, 'for-of': _forOf, 'map': _map}

  if (!selectedOption){
    console.log('no option selected. enter one of the following options:', Object.keys(options).join(', '))
  } else {
    options[selectedOption]()
  }
}

main(process.argv)