API Fetch + Error Handling

Javascript code:

// Fetch with remote-first fallback to local file
(function loadTimeline() {
  var sources = [
    'https://raw.githubusercontent.com/kendawson-online/vantl/refs/heads/main/demo/assets/data/api-fetch-demo-data.json',
    '../../../assets/data/api-fetch-demo-data.json'
  ];

  function renderError(message) {
    var el = document.querySelector('#api-tl');
    el.innerHTML = '
' + message + '
';
  }

  function tryFetch(url) {
    return fetch(url, { cache: 'no-cache' })
      .then(function (res) {
        if (!res.ok) { throw new Error('HTTP ' + res.status); }
        return res.json();
      });
  }

  sources.reduce(function (attempt, url) {
    return attempt.catch(function () { return tryFetch(url); });
  }, Promise.reject())
    .then(function (data) {
      timelineFromData('#api-tl', data.nodes || data, { mode: 'horizontal', minWidth: 700 });
    })
    .catch(function (err) {
      renderError('Failed to load timeline data from all sources.');
      console.error(err);
    });
})();