Yet Another Slider with Transition Effect

const cols = 3;
const main = document.getElementById('main');
let parts = [];
let images = [
    "http://www.devanswer.com/img/nature-1.jpg",
    "http://www.devanswer.com/img/nature-2.jpg",
    "http://www.devanswer.com/img/nature-3.jpg"
];
let current = 0;
let playing = false;
for (let i in images) {
    new Image().src = images[i];
}
for (let col = 0; col < cols; col++) {
    let part = document.createElement('div');
    part.className = 'part';
    let el = document.createElement('div');
    el.className = "section";
    let img = document.createElement('img');
    img.src = images[current];
    el.appendChild(img);
    part.style.setProperty('--x', -100 / cols * col + 'vw');
    part.appendChild(el);
    main.appendChild(part);
    parts.push(part);
}
let animOptions = {
    duration: 2.3,
    ease: Power4.easeInOut
};
function go(dir) {
    if (!playing) {
        playing = true;
        if (current + dir < 0) current = images.length - 1;
        else if (current + dir >= images.length) current = 0;
        else current += dir;
        function up(part, next) {
            part.appendChild(next);
            gsap.to(part, { ...animOptions, y: -window.innerHeight }).then(function () {
                part.children[0].remove();
                gsap.to(part, { duration: 0, y: 0 });
            })
        }
        function down(part, next) {
            part.prepend(next);
            gsap.to(part, { duration: 0, y: -window.innerHeight });
            gsap.to(part, { ...animOptions, y: 0 }).then(function () {
                part.children[1].remove();
                playing = false;
            })
        }
        for (let p in parts) {
            let part = parts[p];
            let next = document.createElement('div');
            next.className = 'section';
            let img = document.createElement('img');
            img.src = images[current];
            next.appendChild(img);
            if ((p - Math.max(0, dir)) % 2) {
                down(part, next);
            } else {
                up(part, next);
            }
        }
    }
}
window.addEventListener('keydown', function (e) {
    if (['ArrowDown', 'ArrowRight'].includes(e.key)) {
        go(1);
    }
    else if (['ArrowUp', 'ArrowLeft'].includes(e.key)) {
        go(-1);
    }
});
function lerp(start, end, amount) {
    return (1 - amount) * start + amount * end
}
const cursor = document.createElement('div');
cursor.className = 'cursor';
const cursorF = document.createElement('div');
cursorF.className = 'cursor-f';
let cursorX = 0;
let cursorY = 0;
let pageX = 0;
let pageY = 0;
let size = 8;
let sizeF = 36;
let followSpeed = .16;
document.body.appendChild(cursor);
document.body.appendChild(cursorF);
if ('ontouchstart' in window) {
    cursor.style.display = 'none';
    cursorF.style.display = 'none';
}
cursor.style.setProperty('--size', size + 'px');
cursorF.style.setProperty('--size', sizeF + 'px');
window.addEventListener('mousemove', function (e) {
    pageX = e.clientX;
    pageY = e.clientY;
    cursor.style.left = e.clientX - size / 2 + 'px';
    cursor.style.top = e.clientY - size / 2 + 'px';
});
function loop() {
    cursorX = lerp(cursorX, pageX, followSpeed);
    cursorY = lerp(cursorY, pageY, followSpeed);
    cursorF.style.top = cursorY - sizeF / 2 + 'px';
    cursorF.style.left = cursorX - sizeF / 2 + 'px';
    requestAnimationFrame(loop);
}
loop();
let startY;
let endY;
let clicked = false;
function mousedown(e) {
    gsap.to(cursor, { scale: 4.5 });
    gsap.to(cursorF, { scale: .4 });
    clicked = true;
    startY = e.clientY || e.touches[0].clientY || e.targetTouches[0].clientY;
}
function mouseup(e) {
    gsap.to(cursor, { scale: 1 });
    gsap.to(cursorF, { scale: 1 });
    endY = e.clientY || endY;
    if (clicked && startY && Math.abs(startY - endY) >= 40) {
        go(!Math.min(0, startY - endY) ? 1 : -1);
        clicked = false;
        startY = null;
        endY = null;
    }
}
window.addEventListener('mousedown', mousedown, false);
window.addEventListener('touchstart', mousedown, false);
window.addEventListener('touchmove', function (e) {
    if (clicked) {
        endY = e.touches[0].clientY || e.targetTouches[0].clientY;
    }
}, false);
window.addEventListener('touchend', mouseup, false);
window.addEventListener('mouseup', mouseup, false);
let scrollTimeout;
function wheel(e) {
    clearTimeout(scrollTimeout);
    setTimeout(function () {
        if (e.deltaY < -40) {
            go(-1);
        }
        else if (e.deltaY >= 40) {
            go(1);
        }
    })
}
window.addEventListener('mousewheel', wheel, false);
window.addEventListener('wheel', wheel, false);