function Pager(tableName, itemsPerPage) {
    this.tableName = tableName;
    this.itemsPerPage = itemsPerPage;
    this.currentPage = 1;
    this.pages = 0;
    this.inited = false;
    this.pagername = null;


    this.showRecords = function(from, to) {
        var rows = document.getElementById(tableName).rows;
        // i starts from 1 to skip table header row
        for (var i = 1; i < rows.length; i++) {
            if (i < from || i > to)
                rows[i].style.display = 'none';
            else
                rows[i].style.display = '';
        }
    }

    this.showPage = function(pageNumber) {
        if (!this.inited) {
            alert("not inited");
            return;
        }

        var oldPageAnchor = document.getElementById(this.pagername).childNodes[this.currentPage * 2];
        if (oldPageAnchor.id == 'pg' + this.currentPage) {
            oldPageAnchor.className = 'pg-selected';
        }

        this.currentPage = pageNumber;
        var newPageAnchor = document.getElementById(this.pagername).childNodes[this.currentPage * 2];
        if (newPageAnchor.id == 'pg' + this.currentPage) {
            newPageAnchor.className = 'pg-normal';
        }

        var from = (pageNumber - 1) * itemsPerPage + 1;
        var to = from + itemsPerPage - 1;
        this.showRecords(from, to);
    }

    this.prev = function() {
        if (this.currentPage > 1)
            this.showPage(this.currentPage - 1);
    }

    this.next = function() {
        if (this.currentPage < this.pages) {
            this.showPage(this.currentPage + 1);
        }
    }

    this.init = function() {
        var rows = document.getElementById(tableName).rows;
        var records = (rows.length - 1);
        this.pages = Math.ceil(records / itemsPerPage);
        this.inited = true;
    }

    this.showPageNav = function(pagerName, positionId) {
        if (!this.inited) {
            alert("not inited");
            return;
        }

        var element = document.getElementById(positionId);
        this.pagername = element.id;

        var pagerHtml = '<span onclick="' + pagerName + '.prev();" class="pg-backward">&nbsp;</span>  ';
        for (var page = 1; page <= this.pages; page++)
            pagerHtml += '<span id="pg' + page + '" class="pg-selected" onclick="' + pagerName + '.showPage(' + page + ');">' + page + '</span>  ';
        pagerHtml += '<span onclick="' + pagerName + '.next();" class="pg-forward">&nbsp;</span>';

        element.innerHTML = pagerHtml;
    }
}