is in view port

gistfile1.txt

$(window).scroll(function(){
			clearTimeout(window.resizedFinished);
			window.resizedFinished = setTimeout(function(){
			    $(".tpl-section").each(function(idx, el){
    				if($(el).isInViewport()){
    					//console.log(idx)
    					$(".sub-menu a").removeClass("active");
    					$(".sub-menu li").eq(idx).children("a").addClass("active")
    				}
    			})
			}, 250);
		})
    
    
$.fn.isInViewport = function() {
    var elementTop = $(this).offset().top;
    var elementBottom = elementTop + $(this).outerHeight();

    var viewportTop = $(window).scrollTop();
    var viewportBottom = viewportTop + $(window).height();

    return elementBottom > viewportTop && elementTop < viewportBottom;
};