Add class to div when scroll in viewport

<script>     jQuery(document).ready(function(){         function isInViewport(dev_prakash_selector) {           var elementTop = jQuery(dev_prakash_selector).offset().top;           var elementBottom = elementTop + jQuery(dev_prakash_selector).outerHeight();           var viewportTop = jQuery(window).scrollTop();           var viewportBottom = viewportTop + jQuery(window).height();           return elementBottom > viewportTop && elementTop < viewportBottom;         }          jQuery(window).scroll(function() {           jQuery('.step_circle li.outer').each(function() { //simply change the selector as per your need             var dev_prakash_selector = jQuery(this);             if (isInViewport(dev_prakash_selector)) {               jQuery(this).addClass("in_viewpport"); //change the "in_viewpport" class name as per your need             } else {               jQuery(this).removeClass("in_viewpport"); //change the "in_viewpport" class name as per your need             }           });         });  }); </script>