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                <div class="accueil"></div>



                .accueil {
  width: 100%;
  height: 200px;
  opacity: 0;
  transition: opacity 3s;

.fadeInAnimation {
  opacity: 1;


                const BACKGROUND_URI = ""
// La fonction suivante va s'exécuter au chargement de la page
window.onload = function () {
  console.log("Fenêtre chargée")
  // On créé une nouvelle image et on demande au navigateur de charger la fichier image source
  let background = new Image()
  background.src = BACKGROUND_URI
  // La fonction suivante va s'exécuter une fois que le navigateur aura chargé l'image
  background.onload = function () {
    console.log("Image chargée")
    // Appliquer le background
    let accueil = document.querySelector(".accueil") = `url(${background.src})`
    // Lancer l'animation