scroll-eventlistener.js

window.addEventListener("load", function() {
  // use slice for supporting IE 11
  Array.prototype.slice.call(document.querySelectorAll('.menu-item')).forEach(item => {
    const target = item.getAttribute('data-id');
    
    item.addEventListener('click', e => {
      e.preventDefault();
      scroll(document.getElementById(target));
    });
    
  })
});