Scripts not working in Safari?

Question

JavaScript

Good afternoon! I made a preloader, after loading the body, the preloader is assigned the done
HTML class:

<div class="hellopreloader" id="page-preloader">
  <div class="loader"></div>
</div>

Javascript:

<script type="text/javascript">


var preloaderDiv = document.getElementById('page-preloader');
var preloader = document.getElementById('page-preloader');
   
      document.body.onload =  function() {
        setTimeout(function () {
          
          if (!preloader.classList.contains('done')) {
            preloader.classList.add('done');
          }
        }, 1000);
        
      }
    </script>

The problem is that in Safari the class is not assigned and the preloader spins forever, in Chrome on the desktop everything is fine, on phones it is not shown at all. What is the reason
By the way, Safari throws such an error in the console

The source list for Content Security Policy directive 'script-src' contains an invalid source: ''strict-dynamic''. It will be ignored.

Answer 1

safari, as far as I remember, does not understand document.body.onload
try window.onload