10-promises.ts

// PromisedNumber :: () -> Promise<number>
const PromisedNumber = () => new Promise(function (fulfill, reject) {
  setTimeout(() => { fulfill(10) }, 500)
})
// PromisedString :: () -> Promise<string>
const PromisedString = () => new Promise(function (fulfill, reject) {
  setTimeout(() => { fulfill(10) }, 1000)
})

console.log('start')

const AsyncPipeline = () => {
  // we don't actually need these two variables
  const promisedNumber = PromisedNumber()
  const promisedString = PromisedString()

  promisedNumber.then(
    (value) => {
      console.log('number: ', value)
      return promisedString
    },
    (err) => { console.log('error: ', err.message) }
  )
  .then(
    (value) => { console.log('string:', value) },
    (err) => { console.log('error:', err.message) }
  )
}

AsyncPipeline()

console.log('finish')