art_y10

var PARRALAX_CONTAINER_HEIGHT_AND_BOTTOM = (document.getElementsByClassName("parallax__cont")[0].scrollHeight + 30);
var PAGE_WITHOUT_BOTTOM = (document.body.scrollHeight - PARRALAX_CONTAINER_HEIGHT_AND_BOTTOM);
  var el = document.querySelector('.parallax__back');
  var parentEl = document.querySelector('.parallax__cont');

  window.addEventListener('scroll', function(){
    if(window.pageYOffset > parentEl.offsetTop) {
      if ( el.classList.contains('is-active') != true ) {
        el.classList.add('is-active');
      }
      if(window.pageYOffset > PAGE_WITHOUT_BOTTOM) {
        //console.log(window.pageYOffset);
        //console.log(PAGE_WITHOUT_BOTTOM);
        el.classList.remove('is-active');
        el.classList.add('is-bottom');
      }
    } else {
      if ( el.classList.contains('is-active') == true ) {
        el.classList.remove('is-active');
      }
      if ( el.classList.contains('is-bottom') == true ) {
        el.classList.remove('is-bottom');
      }
    }
    //console.log(PARRALAX_CONTAINER_HEIGHT_AND_BOTTOM);
    //console.log(PAGE_WITHOUT_BOTTOM);
  })
});