async-await.js

function getMockDelay() {
  return 1000 + (Math.random() * 4000);
}

async function getProducts() {
  return new Promise((resolve) => {
    var products = [
      {title: 'Wave Runner', category: 'sports', cost: 5000},
      {title: 'Mac', category: 'electronics', cost: 2000},
      {title: 'Toaster', category: 'kitchen', cost: 10},
      {title: 'Cereal', category: 'kitchen', cost: 5},
      {title: 'Nike Shoes', category: 'clothing', cost: 50}
    ];
    setTimeout(() => {resolve(products)}, getMockDelay());
  });
}

async function getCustomerBalance() {
  return new Promise((resolve) => {
    let mockBalance = 4000; 
    setTimeout(() => resolve(mockBalance), getMockDelay());
  });
}

async function getCustomerPrefs() {
  return new Promise((resolve) => {
    let preferences = ['electronics','clothing'];
    setTimeout(() => resolve(preferences), getMockDelay());
  });
}

(async function showRecommendations() {
  let products = await getProducts();
  let balance = await getBalance();
  let prefs = await getCustomerPrefs();

  let relevantProducts = products
    .filter((product) => (product.cost <= balance))
    .filter((product) => (prefs.indexOf(product.category) !== -1));

  console.assert(relevantProducts.length === 1);
  console.log('Relevant Products: %o', relevantProducts);
})();