Type ahead functionality

This code was taken from JavaScript30 by Wes Bos. This funcionality is common in applications so its handy to have as a code snippet!

//Get all cities in an array from a json file
const endpoint = 'https://gist.githubusercontent.com/Miserlou/c5cd8364bf9b2420bb29/raw/2bf258763cdddd704f8ffd3ea9a3e81d25e2c6f6/cities.json';
const cities = [];
.then(blob => blob.json())
.then(data => cities.push(...data));
//Filter the one we want based on a regex
function findMatches(matchedWord, cities) {
  return cities.filter(place => {
    //check what city or state matches
    const regex = new RegExp(matchedWord, 'gi');
    return place.city.match(regex) || place.state.match(regex)
function numberWithCommas(x) {
    return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
function displayMatches() {
  const searchPhrase = this.value;
  const matchArray = findMatches(searchPhrase, cities);
  const html = matchArray.map(place => {
    const regexHi = new RegExp(this.value, 'gi');
    const cityName = place.city.replace(regexHi, `<span class="hl">${this.value}</span>`);
    const cityState = place.state.replace(regexHi, `<span class="hl">${this.value}</span>`);
    return `<li>
        <span class="name">${cityName}, ${cityState}</span>
        <span class="population">${numberWithCommas(place.population)}</span>

  suggestions.innerHTML = html;

const searchInput = document.querySelector('.search');
const suggestions = document.querySelector('.suggestions');

searchInput.addEventListener('change', displayMatches);
searchInput.addEventListener('keyup', displayMatches);

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