how to prevent exit full mode when changing url in js

i made a button to full screen mode in my web page using js , but whenever i switch the url the full screen exit !? but when i use F11 to full screen it works fine! ?

<script>
  function getFullscreenElement(){
    return document.fullscreenElement 
    || document.webkitFullscreenElement
    || document.mozFullscreenElement
    || document.msFullscreenElement;
  }

  function toggleFullscreen(){
    if (getFullscreenElement()) {
      document.exitFullscreen();
    }else{
      document.documentElement.requestFullscreen().catch(console.log(e));
    }
  }

  document.getElementById('expand').addEventListener('click',function() {
    toggleFullscreen();
    });

</script>

<p id="expand"><i title='full screen' class="fas fa-expand-arrows-alt"></i></p>

it there something i have missed !? thank you ..