Best scroll into view script

/*
usage: scrollToElm($containerElement.get(0), $targetItem.get(0), 0.2);
url: https://stackoverflow.com/a/51005649
*/

function scrollToElm(container, elm, duration) {
    var pos = getRelativePos(elm);
    scrollTo(container, pos.top, duration);  // duration in seconds
}

function getRelativePos(elm) {
    var pPos = elm.parentNode.getBoundingClientRect(), // parent pos
        cPos = elm.getBoundingClientRect(), // target pos
        pos = {};

    pos.top = cPos.top - pPos.top + elm.parentNode.scrollTop;
    pos.right = cPos.right - pPos.right;
    pos.bottom = cPos.bottom - pPos.bottom;
    pos.left = cPos.left - pPos.left;

    return pos;
}

function scrollTo(element, to, duration, onDone) {
    var start = element.scrollTop,
        change = to - start,
        startTime = performance.now(),
        val, now, elapsed, t;

    function animateScroll() {
        now = performance.now();
        elapsed = (now - startTime) / 1000;
        t = (elapsed / duration);

        element.scrollTop = start + change * easeInOutQuad(t);

        if (t < 1)
            window.requestAnimationFrame(animateScroll);
        else
            onDone && onDone();
    };

    animateScroll();
}

function easeInOutQuad(t) {
    return t < .5 ? 2 * t * t : -1 + (4-2 * t) * t
};