Promise

promise-chain-test.js

Promise.resolve(100).then(num => {
  console.log('num: ', num);
  return num + 100;
}).then(num => {
  console.log('num2:', num);
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log('timeout');
      resolve('World');
    }, 1000);
  })
}).then(message => {
  console.log('Hello ', message);
});