Make element sticky to the viewport when scroll

sticky.js

function setSticky(elementId) {
  const stickyElement = document.getElementById(elementId)
  const stickyTop = stickyElement.offsetTop

  const setStickyClass = () => {
    if (window.pageYOffset > stickyTop) {
      stickyElement.classList.add('sticky')
    } 
    else {
      stickyElement.classList.remove('sticky')
    }		  	
  }

  window.onscroll = setStickyClass

  return setStickyClass
}	

// setSticky('elementIdSelector')

/*
// CSS
.sticky {
  position: fixed;
  top: 0;
  max-height: 100vh;
  overflow-y: scroll;
}
*/