Scroll window to position (copied from somewhere (don't remember where)). Is a useful script (this version is slightly updated from the original to take into account float values in modern browser and also clear the animation frame (old version didn't do that)).

scrollWindowTo.js

import {isset} from 'fjl';

const easings = {
    linear(t) {
        return t;
    },
    easeInQuad(t) {
        return t * t;
    },
    easeOutQuad(t) {
        return t * (2 - t);
    },
    easeInOutQuad(t) {
        return t < 0.5 ? 2 * t * t : -1 + (4 - 2 * t) * t;
    },
    easeInCubic(t) {
        return t * t * t;
    },
    easeOutCubic(t) {
        return (--t) * t * t + 1;
    },
    easeInOutCubic(t) {
        return t < 0.5 ? 4 * t * t * t : (t - 1) * (2 * t - 2) * (2 * t - 2) + 1;
    },
    easeInQuart(t) {
        return t * t * t * t;
    },
    easeOutQuart(t) {
        return 1 - (--t) * t * t * t;
    },
    easeInOutQuart(t) {
        return t < 0.5 ? 8 * t * t * t * t : 1 - 8 * (--t) * t * t * t;
    },
    easeInQuint(t) {
        return t * t * t * t * t;
    },
    easeOutQuint(t) {
        return 1 + (--t) * t * t * t * t;
    },
    easeInOutQuint(t) {
        return t < 0.5 ? 16 * t * t * t * t * t : 1 + 16 * (--t) * t * t * t * t;
    }
};

let rqAnimationFrame;

export function scrollWindowTo (destination, duration = 200, easing = 'linear', callback) {
    const start = window.pageYOffset;
    const startTime = 'now' in window.performance ? performance.now() : new Date().getTime();
    const {body, documentElement} = document;
    const documentHeight = Math.max(
        body.scrollHeight,
        body.offsetHeight,
        documentElement.clientHeight,
        documentElement.scrollHeight,
        documentElement.offsetHeight
    );
    const windowHeight = window.innerHeight || documentElement.clientHeight || body.clientHeight;
    const destinationOffset = typeof destination === 'number' ? destination : destination.offsetTop;
    const destinationOffsetToScroll = Math.round(documentHeight - destinationOffset < windowHeight ? documentHeight - windowHeight : destinationOffset);

    if ('requestAnimationFrame' in window === false) {
        window.scroll(0, destinationOffsetToScroll);
        if (callback) {
            callback();
        }
        return;
    }

    function scroll() {
        const now = 'now' in window.performance ? performance.now() : new Date().getTime();
        const time = Math.min(1, ((now - startTime) / duration));
        const timeFunction = easings[easing](time);
        window.scroll(0, Math.ceil((timeFunction * (destinationOffsetToScroll - start)) + start));
        console.log(Math.round(window.pageYOffset), destinationOffsetToScroll)
        if (Math.round(window.pageYOffset) === destinationOffsetToScroll) {
            if (callback) {
                callback();
            }
            if(isset(rqAnimationFrame)) {
                cancelAnimationFrame(rqAnimationFrame);
            }
            return;
        }
        rqAnimationFrame = requestAnimationFrame(scroll);
    }

    cancelAnimationFrame(rqAnimationFrame);
    scroll();
}

export default scrollWindowTo