Alert when div is visible during scrolling

some.js

// hide the navbar when reached bottom
  window.addEventListener('scroll', function() {
  	var element = document.querySelector('.site-footer');
  	var position = element.getBoundingClientRect();
  	// checking whether fully visible
  	if(position.top >= 0 && position.bottom <= window.innerHeight) {
  		// console.log('Element is fully visible in screen');
  	}else{
      $('.navbar').slideDown();
    }
  	// checking for partial visibility
  	if(position.top < window.innerHeight && position.bottom >= 0) {
  		// console.log('Element is partially visible in screen');
  	}else{
    }
  });