how to set number pagination [div pagination jquery system]

Hy I have following tutorial pagination jquery system

here for demo http://ift.tt/1DAW9Lq

This my code :

$(document).ready(function() {

    var show_per_page = 1;
    var number_of_items = $('#list').children('li').size();
    var number_of_pages = Math.ceil(number_of_items / show_per_page);

    $('body').append('<div class=controls></div><input id=current_page type=hidden><input id=show_per_page type=hidden>');
    $('#current_page').val(0);
    $('#show_per_page').val(show_per_page);

    var navigation_html = '<a class="prev" onclick="previous()">Prev</a>';
    var current_link = 0;
    while (number_of_pages > current_link) {
        navigation_html += '<a class="page" onclick="go_to_page(' + current_link + ')" longdesc="' + current_link + '">' + (current_link + 1) + '</a>';
        current_link++;
    }
    navigation_html += '<a class="next" onclick="next()">Next</a>';

    $('.controls').html(navigation_html);
    $('.controls .page:first').addClass('active');

    $('#list').children().css('display', 'none');
    $('#list').children().slice(0, show_per_page).css('display', 'block');

});



function go_to_page(page_num) {
    var show_per_page = parseInt($('#show_per_page').val(), 0);

    start_from = page_num * show_per_page;

    end_on = start_from + show_per_page;

    $('#list').children().css('display', 'none').slice(start_from, end_on).css('display', 'block');

    $('.page[longdesc=' + page_num + ']').addClass('active').siblings('.active').removeClass('active');

    $('#current_page').val(page_num);
}



function previous() {

    new_page = parseInt($('#current_page').val(), 0) - 1;
    //if there is an item before the current active link run the function
    if ($('.active').prev('.page').length == true) {
        go_to_page(new_page);
    }

}

function next() {
    new_page = parseInt($('#current_page').val(), 0) + 1;
    //if there is an item after the current active link run the function
    if ($('.active').next('.page').length == true) {
        go_to_page(new_page);
    }

}

.controls a{
    padding:3px;
    border:1px solid gray;
    margin:2px;
    color:black;
    text-decoration:none
}
.active{
    background:darkblue;
    color:white !important;
}

<script src="http://ift.tt/JJs6bh"></script>
<ul id=list>
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
    <li>Item 4</li>
    <li>Item 5</li>
    <li>Item 6</li>
    <li>Item 7</li>
    <li>Item 8</li>
    <li>Item 9</li>
    <li>Item 10</li>
</ul>

My quetion is how display just 4 number in pagination, for example :
I have 10 data
show_per_page = 1;
display number in pagination 1,2,3,4 next and if I'm click next display number 5,6,7,8 next,
prev 9,10
Thanks