let wait = false;

function setBackground(url) {
  if (wait) return;
  if (background.getAttribute("src") == url) return;
  wait = true;
  let newBackground = document.createElement("img")
  newBackground.id = "newBackground"
  newBackground.className = "background"
  newBackground.style.opacity = 0
  newBackground.style.zIndex = -90
  newBackground.src = url
  background.after(newBackground)
  function start(){ console.log("start"); newBackground.style.opacity = 1 }
  function end(){
    console.log("end")
    background.remove()
    newBackground.id = "background"
    newBackground.style.zIndex = -100
    background = document.getElementById("background")
    wait = false;
  }

  newBackground.addEventListener("transitionend", end)
  //setTimeout(end, 2000);
  newBackground.addEventListener("load", () => {
    setTimeout(start, 10);
  })
}
document.addEventListener("DOMContentLoaded", function(){
  background = document.getElementById("background")
})