script.js

function smoothScroll(target, duration) {
  let target1 = document.querySelector(target);
  let targetPosition = target1.getBoundingClientRect().top;
  let startPosition = window.pageYOffset;
  let distance = targetPosition - startPosition;
  let startTime = null;

  function animation(currentTime) {
    if (startTime === null) {
      startTime = currentTime;
    }
    let timeElapsed = currentTime - startTime;
    let run = ease(timeElapsed, startPosition, distance, duration);
    window.scrollTo(0, run);
    if (timeElapsed < duration) {
      requestAnimationFrame(animation);
    }
    console.log({ timeElapsed, duration });
  }

  function ease(t, b, c, d) {
    t /= d / 2;
    if (t < 1) return (c / 2) * t * t + b;
    t--;
    return (-c / 2) * (t * (t - 2) - 1) + b;
  }

  requestAnimationFrame(animation);
}

const section1 = document.querySelector(".section1");
const section2 = document.querySelector(".section2");

section1.addEventListener("click", function() {
  smoothScroll(".section2", 1000);
});

section2.addEventListener("click", function() {
  smoothScroll(".section1", 1000);
});