player.js

{  
  // DOM
  const script = document.currentScript;
  let canvas = document.getElementById('canvas');
  if (!canvas) {
    canvas = document.createElement('CANVAS');
    canvas.id = 'canvas';
    script.parentNode.insertBefore(canvas, script);
  }
  canvas.oncontextmenu = () => event.preventDefault();
  let spinner = document.getElementById('spinner');
  if (!spinner) {
    spinner = document.createElement('DIV');
    spinner.id = 'spinner';
    script.parentNode.after(spinner, script);
  }
  spinner.className = 'pending';
  
  // Parse arguments from the URL address
  let url = new URL(script.src);
  if (!url.searchParams.has('g'))
    url = new URL(window.location.href);
  let arg = url.searchParams.get('arg');
  let uri = url.searchParams.get('g');
  let compat = url.searchParams.get('c');
  let version = url.searchParams.get('v');

  if (uri == null)
    uri = 'nogame.love';
  if (arg) {
    try {
      arg = JSON.parse(arg);
      if (!Array.isArray(arg))
        arg = [arg];
    } catch (error) {
      arg = null;
      console.log(error);
    }
  }

  import('./game.js')
    .then((imported) => {
      const load = imported.default;

      // Runs the requested package
      window.runLove = () => {
        //state = 'loading';
        spinner.className = 'loading';
        load(canvas, uri, arg, version, compat)
          .then((res) => {
            canvas.style.display = 'block';
            canvas.focus();
            //state = 'playing';
            spinner.className = '';
          })
          .catch((err) => {
            console.log(err);
            if (uri != 'nogame.love') {
              uri = 'nogame.love';
              arg = null;
              window.runLove();
            }
          });
      }
      
      // Handling errors
      //window.alert = window.onerror = (msg) => {
      window.onerror = (msg) => {
        console.log(msg);
        if (spinner.className != '') {
          canvas.style.display = 'none';
          spinner.className = 'error';
        }
      };

      // Focus when running inside an iFrame
      window.onload = window.focus.bind(window);
      
      // Handle touch and mouse input
      window.onclick = (e) => {
        window.focus();
      };

      // Disable window scrolling using the arrow keys
      const prevent = [37, 38, 39, 40, 13];
      window.onkeydown = (e) => {
        if (prevent.indexOf(e.keyCode) > -1)
          e.preventDefault();
      }

      // Fixes a persistence bug when using the back and forward buttons
      window.onpageshow = (event) => {
        canvas.style.display = 'none';
        if (event.persisted)
          window.location.reload();
      };
      
      if (!window.SharedArrayBuffer) {
        //alert('The Cross-Origin Policy is not configured properly');
        throw new Error('The Cross-Origin Policy is not configured properly');
        return;
      }
      
      window.runLove();
    });
};