kahoot.js

document.onkeydown = function(e){
  switch(e.key) {
    case "1":
      document.querySelectorAll("button.answerA")[0].click();
      break;
    case "2":
      document.querySelectorAll("button.answerB")[0].click();
      break;
    case "3":
      document.querySelectorAll("button.answerC")[0].click();
      break;
    case "4":
      document.querySelectorAll("button.answerD")[0].click();
      break;
  }
}