Unity isn’t as bad as I though.

<script src="TemplateData/UnityProgress.js"></script>  
<script src="Build/UnityLoader.js"></script>
<script>
  var gameInstance = UnityLoader.instantiate("gameContainer", "Build/WebGL.json", {onProgress: UnityProgress});
</script> <script> var gameInstance = UnityLoader.instantiate("gameContainer", "Build/WebGL.json", {onProgress: UnityProgress}); </script>