hello_world_async.js

import 'babel-core/register';
import 'babel-polyfill';

function getRandom(from, to, callback) {
  setTimeout(() => {
    const value = Math.floor((Math.random() * (to - from + 1)) + from);
    callback(value);
  }, 500);
}

function sum(x, y, callback) {
  setTimeout(() => {
    callback(x + y);
  }, 250);
}

function display(value, callback) {
  setTimeout(() => {
    console.log(value);
    callback(true);
  }, 100);
}

getRandom(1, 6, (value) => {
  sum(value, 10, (total) => {
    display(total, (success) => {
      console.log('callback', success);
    });
  });
});

const Promised = {
  getRandom(from, to) {
    return new Promise((resolve) => {
      getRandom(from, to, (value) => {
        resolve(value);
      });
    });
  },
  sum(x, y) {
    return new Promise((resolve) => {
      sum(x, y, (value) => {
        resolve(value);
      });
    });
  },
  display(value) {
    return new Promise((resolve) => {
      display(value, (success) => {
        resolve(success);
      })
    });
  }
}

Promised.getRandom(1, 6)
  .then((value) => {
    return Promised.sum(value, 10);
  })
  .then((total) => {
    return Promised.display(total);
  })
  .then((success) => {
    console.log('promise', success);
  });

async function main() {
  const random = await Promised.getRandom(1, 6);
  const total = await Promised.sum(random, 10);
  const success = await Promised.display(total);
  console.log('async/await', success);
}
main();

console.log('start');