Promise-pre-work.md

#Promise Practice

  return new Promise((resolve, reject) => {
    if(num > 10) {
      resolve(`${num} is greater than 10`)
    } else {
      reject(Error(`${num} is less than 10`))
    }
  })
}

testNum(90)
  .then(result => console.log(result))
  .catch(err => console.error(err))

const words = ['cheese', 'bread', 'salami', 'apple'];

function makeAllCaps(words) {
  return new Promise((resolve, reject) => {
    if(words.every(val => typeof val === 'string')) {
      resolve(words.map(word => word.toUpperCase()))
    } else {
      reject(Error('Strings only please!'))
    }
  })
}

function sortWords(words) {
  return new Promise((resolve, reject) => {
      resolve(words.sort())
  })
}

makeAllCaps(words)
  .then(words => sortWords(words))
  .then(result => console.log(result))
  .catch(err => console.error(err))

.then() is used to perform an action with a resolved promise object whereas .catch() is used to perform an action with a rejected promise.
Any kind of async code would be a good case for a promise but using it along side a fetch has been essential.
Promises can be used in frameworks like Angular and react as well as other libraries like jQuery.

N-Gibson/Promise-pre-work.md