Scroll document to any vertical position with smooth animation without any library.

animate-body-vertical-scroll.js

const easeInQuad = (t, b, c, d) => {
	return c * (t /= d) * t + b;
}

const requestAnimFrame = (() => {
  return  window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function( callback ){ window.setTimeout(callback, 1000 / 60); };
})();

export const scrollBodyTo = (to, duration = 400, callback) => {
	const move = (amount) => {
    document.documentElement.scrollTop = amount;
    document.body.parentNode.scrollTop = amount;
    document.body.scrollTop = amount;
  }
  const position = () => {
    return document.documentElement.scrollTop || document.body.parentNode.scrollTop || document.body.scrollTop;
  }
	const getDocHeight = () => {
    return Math.max(
        document.body.scrollHeight, document.documentElement.scrollHeight,
        document.body.offsetHeight, document.documentElement.offsetHeight,
        document.body.clientHeight, document.documentElement.clientHeight
    );
	}

	const start = position();
  const change = to - start;
	const increment = 50;

  let currentTime = 0;

  const animateScroll = () => {
    currentTime += increment;
    /* You can use any easing function here */ 
    let val = easeInQuad(currentTime, start, change, duration);
    move(val);
    if (currentTime < duration) {
      requestAnimFrame(animateScroll, increment);
    } else {
			if (position() <= 0) {
				move(0);
			}
			if (position() >= getDocHeight()) {
				move(getDocHeight());
			}
			callback && typeof callback === 'function' && callback();
		}
  };
  animateScroll();
}

Call scrollBodyTo method with params

to: position to scroll body
duration: optional duration in ms to animate scrolling (defaults: 400ms)
callback: optional callback to be called after animation is fininshed

scrollBodyTo(400, 500, ()=>{console.log('scrolling animation finished')})