Swipes handling with vanilla js

swipevanilla.js

var touchstartX = 0;
var touchstartY = 0;
var touchendX = 0;
var touchendY = 0;

var swipeme = document.getElementById('swipeme');

swipeme.addEventListener('touchstart', function(event) {
    touchstartX = event.changedTouches[0].screenX;
    touchstartY = event.changedTouches[0].screenY;
}, false);

swipeme.addEventListener('touchend', function(event) {
    touchendX = event.changedTouches[0].screenX;
    touchendY = event.changedTouches[0].screenY;
    handleGesture();
}, false); 

function handleGesture() {
    var swiped = 'swiped: ';
    if (touchendX < touchstartX) {
        alert(swiped + 'left!');
    }
    if (touchendX > touchstartX) {
        alert(swiped + 'right!');
    }
    if (touchendY < touchstartY) {
        alert(swiped + 'down!');
    }
    if (touchendY > touchstartY) {
        alert(swiped + 'left!');
    }
    if (touchendY == touchstartY) {
        alert('tap!');
    }
}