Callback functions -> promises -> generator functions

evolution-of-asynchrony.js

// Callback functions
function fetchData() {
  this.fetch('data', (data) => {
    this.updateUI();
  });
}

// Promises
function fetchData() {
  this.fetch('data')
    .then((data) => {
      this.updateUI();
    });
}

// Generator functions
function * fetchData() {
  const data = yield this.fetch('data');
  this.updateUI();
}