Firefox PDF.js reader autoscroll shorcuts

Firefox_PDFjs_reader_autoscroll.js

// use the s shortcut to toggle autoscroll 
var as; document.onkeyup = function(e) {
  if(e.key == "s"){
    if (!as) {
      as = setInterval( () => { document.querySelector("#viewerContainer").scrollBy(0, 1) } , 100 );
      // for a normal page use window.scrollBy instead
    } else {
      clearInterval(as); as = null; scrolling = false;
    }
  }
}
// example GIF https://twitter.com/utopiah/status/1101890549504724993