Utilities for easing and animation ala jquery but vanilla javascript

utils.js

// easing equations from https://github.com/danro/easing-js/blob/master/easing.js
export const EASING = {
  linear: x => x,
  easeOut: x => Math.sin(x * (Math.PI / 2)),
  easeInOut: x => (-0.5 * (Math.cos(Math.PI * x) - 1)),
  easeInOutQuint: x => (x /= 0.5) < 1 ? 0.5 * Math.pow(x, 5) : 0.5 * (Math.pow((x - 2), 5) + 2)
};

export const animate = (method, ms = 1000, ease = EASING.easeInOut) => {
  const now = () => (window.performance || Date).now();
  const startTime = now();

  const step = () => {
    let time = (now() - startTime);
    time = time > ms ? ms : time;

    method(ease(time / ms));

    if (time < ms) {
      requestAnimationFrame(step);
    }
  };

  requestAnimationFrame(step);
};

export const scrollToElement = ({ element, offset = 0, ms, ease }) => {
  const navHeight = document.querySelector('.uebp-header-sticky').offsetHeight;
  const baseY = window.scrollY;
  const difference = element.offsetTop - offset - navHeight - baseY;

  animate(x => scrollTo(0, baseY + difference * x), ms, ease);
};