Working on demonstrating Promises

promises.js

// Without Promises
setTimeout(function() {
  console.log('first thing');
  setTimeout(function() {
    console.log('then second');
    setTimeout(function() {
      console.log('and now the third')
    }, 1000);
  }, 1000)
}, 1000);

// With Promises
delay(1000)
.then(() => {
  console.log('first thing');
  return delay(1000);
})
.then(() => {
  console.log('then second');
  return delay(1000);
})
.then(() => {
  console.log('and now the third');
  return delay(1000);
})
.catch(() => {
  console.log('error!')
});


function delay(wait) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(), wait);
  })
};


// Now an array of Promises
let promises = [];

promises.push(delay(1000));
promises.push(delay(3000));
promises.push(delay(2000));
promises.push(delay(2000));

let allDone = Promise.all(promises);

allDone.then(() => {
  console.log('All finished');
})
.catch(() => {
  console.log('error!')
});


function delay(wait) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(), wait);
  })
};