promises are fun.

promises-are-fun.js

// this is coming from a library
function delayedValue(x) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(x), 1000)
  })
}

// module doQuery.js
function doQuery() {
  return delayedValue({
    name: 'my result',
    values: [1, 2, 3, 4, 5],
  }).then(result => {
    if (result.error) {
      throw new Error('doQuery error: ' + result.error)
    }
    console.log('doQuery: result is: ', result)

    return result
  })
}

function subQuery(value) {
  return delayedValue(value * value)
}

// module.exports = { doQuery };

// elsewhere:
// const doQuery = require('doQuery')

var p1 = doQuery()

p1
  .then(x => {
    x['abc'] = 123
    console.log(x)
    return x
  })
  .then(x => {
    const promises = x.values.map(value => subQuery(value))
    return Promise.all(promises)
  })
  .catch(error => {
    console.error('did query, got error', error)
    return { name: 'foo' }
  })
  .then(values => {
    for (let value of values) {
      console.log('value: ', value)
    }
  })

// p1.then(x => {
//   console.log('this is the other one')
// })