[Retro_1477]

Спасибо вам за помощь!
Код теперь выглядит так

var button1, button2;

var el = document.getElementsByTagName('body')[0];

  el.addEventListener("touchstart", handler, false);
  el.addEventListener("touchend", handleEnd, false);
  el.addEventListener("touchmove", handler, false);

function handler(e) {
    button2 = !(button1 = (window.innerWidth / 2) < e.changedTouches[0].pageX);
};
function handleEnd(e) {
  var touches = e.changedTouches;
  if (window.innerWidth / 2 < touches[0].pageX)
    button1 = false;
  button2 = false;
  if (window.innerWidth / 2 > touches[0].pageX) {
    button2 = false;
    button1 = false
  }
};