scroll a full page height up or down with jQuery/Javascript

HTML :-

     <div class="div" style="text-align: center; color: green">

            Gallery</div>

        <div class="div" style="background-color: #aaa">

            Page 1</div>

        <div class="div" style="background-color: #444">

            Page 2</div>

        <div class="div" style="background-color: blue">

            Page 3</div>

        <div class="div" style="background-color: #ccc">

            Page 4</div>

        <div class="div" style="background-color: pink">

            Page 5</div>

Script : -

<script language="javascript" type="text/javascript">

        $(document).ready(function() {

            var divs = $('.div');

            divs.css('height',$( document ).height());

            var dir = 'up'; // wheel scroll direction

            var div = 0; // current div

            $(document.body).on('DOMMouseScroll mousewheel', function(e) {

                if (e.originalEvent.detail > 0 || e.originalEvent.wheelDelta < 0) {

                    dir = 'down';

                } else {

                    dir = 'up';

                }

                // find currently visible div :

                div = -1;

                divs.each(function(i) {

                    if (div < 0 && ($(this).offset().top >= $(window).scrollTop())) {

                        div = i;

                    }

                });

                if (dir == 'up' && div > 0) {

                    div--;

                }

                if (dir == 'down' && div < divs.length) {

                    div++;

                }

                //console.log(div, dir, divs.length);

                $('html,body').stop().animate({

                    scrollTop: divs.eq(div).offset().top

                }, 200);

                return false;

            });

            $(window).resize(function() {

                $('html,body').scrollTop(divs.eq(div).offset().top);

            });

        });

    </script>