Accurate and simple way to detect swipes in vanilla js.

swiper2.js

let start = null
let end = null;
const el = document.body;

el.addEventListener('touchstart', event => start = event.changedTouches[0], false);
el.addEventListener('touchend', event => {
    end = event.changedTouches[0];

    let hr = (end.screenX - start.screenX) / el.getBoundingClientRect().width;
    let vr = (end.screenY - start.screenY) / el.getBoundingClientRect().height;

    if (hr > vr && hr > 0.25) return console.log('right');
    if (hr < vr && hr < -0.25) return console.log('left');
    if (vr > hr && vr > 0.25) return console.log('down');
    if (vr < hr && vr < -0.25) return console.log('up');
}, false);