FadeIn on Scroll (jQuery)

Used to answer a question on StackOverflow.

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

$(window).on("load",function() {
  function fade(pageLoad) {
    var windowTop=$(window).scrollTop(), windowBottom=windowTop+$(window).innerHeight();
    var min=0.3, max=0.7, threshold=0.01;
    
    $(".fade").each(function() {
      /* Check the location of each desired element */
      var objectHeight=$(this).outerHeight(), objectTop=$(this).offset().top, objectBottom=$(this).offset().top+objectHeight;
      
      /* Fade element in/out based on its visible percentage */
      if (objectTop < windowTop) {
        if (objectBottom > windowTop) {$(this).fadeTo(0,min+((max-min)*((objectBottom-windowTop)/objectHeight)));}
        else if ($(this).css("opacity")>=min+threshold || pageLoad) {$(this).fadeTo(0,min);}
      } else if (objectBottom > windowBottom) {
        if (objectTop < windowBottom) {$(this).fadeTo(0,min+((max-min)*((windowBottom-objectTop)/objectHeight)));}
        else if ($(this).css("opacity")>=min+threshold || pageLoad) {$(this).fadeTo(0,min);}
      } else if ($(this).css("opacity")<=max-threshold || pageLoad) {$(this).fadeTo(0,max);}
    });
  } fade(true); //fade elements on page-load
  $(window).scroll(function(){fade(false);}); //fade elements on scroll
});