subscribe-to-combine.js

// Subscribe to the latest stream that contains both 
// California and Colorado.
californiaOrColorado$.subscribe((result) => {
  // Output to UI.
  var citiesEle = document.getElementById('cities');
  result.forEach(city => {
      var itemEle = document.createElement("li");
      itemEle.textContent = city.name;
      citiesEle.appendChild(itemEle);
    });
})