allaroundhere.org/js/custom.js

const BACKGROUND_IMAGES = [
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-allis.jpg",
    description: "Allis Engine #4, Metropolitan Waterworks Museum",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-boston.jpg",
    description: "Charles River Basin and Skyline",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-denver.jpg",
    description: "Mile-High City Skyline",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-geese.jpg",
    description: "Geese and Goslings on the banks of the Charles River",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-hotel.jpg",
    description: "Bay Point Hotel, Lake Winnipesaukee",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-lawrencedam.jpg",
    description: "Hydroelectric Dam on the St. Lawrence River",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-letchworth.jpg",
    description: "The Middle Falls in Letchworth State Park",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-library.jpg",
    description: "Robert W. Woodruff Library at Emory University",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-lighthouse.jpg",
    description: "Nubble Lighthouse",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-mbta.jpg",
    description: "Old vs New MBTA Green Line",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-rockyshore.jpg",
    description: "Icy Stormy Shoreline at Brenton Point",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-rt112.jpg",
    description: "Northern end of the Route 112 Scenic Byway",
    source: ""
  },
  {
    url: "https://cdn.enp.one/img/backgrounds/cl-photo-startrek.jpg",
    description: "Enterprise Engineering Systems at the Star Trek Set Museum",
    source: ""
  }
];


function selectBackground() {
  let max = BACKGROUND_IMAGES.length - 1
  let min = 0;
  index = Math.round(Math.random() * (max - min) + min);
  console.log("Loading background #" + index + ": " + BACKGROUND_IMAGES[index].url);
  return BACKGROUND_IMAGES[index];
}


function togglePrimaryText() {
  let items = document.getElementsByClassName("article");

  for (index = 0; index < items.length; index++) {
    if (items[index].classList.contains("primary-text")) {
      items[index].classList.remove("primary-text");
    } else {
      items[index].classList.add("primary-text");
    }
  }

  let button = document.getElementById("toggle-description");

  if (button.classList.contains("active")) {
    button.classList.remove("active");
  } else {
    button.classList.add("active");
  }
};

window.addEventListener("DOMContentLoaded", function () {
  let selected = selectBackground()

  document.getElementById(
    "background-image"
  ).style.backgroundImage = "url(" + selected.url + ")";
});


window.addEventListener("load", async function () {
  document.getElementById("toggle-description").addEventListener("click", togglePrimaryText);
  document.getElementById("preloader").classList.add("fadeout");
  //  I don't actually know how promises or async works
  //  ¯\_(ツ)_/¯
  // https://stackoverflow.com/questions/951021/what-is-the-javascript-version-of-sleep
  await new Promise(r => setTimeout(r, 250))
  document.getElementById("preloader").style.display = "none";
});