Fade In/Out, Custom Start/Stop Opacity on Scroll

by Matthew Schenker

HTML

<div>
  <div class="fade">Fade In 01</div>
  <div class="fade">Fade In 02</div>
  <div class="fade">Fade In 03</div>
  <div class="fade">Fade In 04</div>
  <div class="fade">Fade In 05</div>
  <div class="fade">Fade In 06</div>
  <div class="fade">Fade In 07</div>
  <div class="fade">Fade In 08</div>
  <div class="fade">Fade In 09</div>
  <div class="fade">Fade In 10</div>
</div>

CSS

.fade {
  margin: 50px;
  padding: 50px;
  background-color: lightgreen;
  opacity: 1;
}

JavaScript

$(window).on("load",function() {
  function fade(pageLoad) {
  	var windowBottom = $(window).scrollTop() + $(window).innerHeight();
    var min = 0.5;
    var max = 1;
    var threshold = 0;
    
    $(".fade").each(function() {
      /* Check the location of each desired element */
      var objectBottom = $(this).offset().top + $(this).outerHeight();
      
      /* If the element is completely within bounds of the window, fade it in */
      if (objectBottom < windowBottom) { //object comes into view (scrolling down)
        if ($(this).css("opacity")<=min+threshold || pageLoad) {$(this).fadeTo(500,max);}
      } else { //object goes out of view (scrolling up)
        if ($(this).css("opacity")>=max-threshold || pageLoad) {$(this).fadeTo(500,min);}
      }
    });
  } fade(true); //fade elements on page-load
  $(window).scroll(function(){fade(false);}); //fade elements on scroll
});