How to integrate "items per page" and "pagination"_问答_开发者

I've written the following codes. The idea is to pass the selected value of "Reports per page" into javascript pagination functions to display the pages accordingly.

Problem: value seemingly passed correctly but pages not displaying properly. E.g. value for "reports per page" = 2. But instead of displaying 2 reports per page, all/total reports were displayed and 2 reports were deducted when "NEXT" is clicked each time / moving from page 1 to 2, etc.

Can anyone advise what is wrong with my codes? Thanks!

      <table>
        <tr>
          <td><label id="lDisplayPerPg" for="lDisplayPerPg">Reports per page</label>
            <select name="listDisplayPerPg" id="listDisplayPerPg">
              <option value="2" selected="selected">2</option>
              <option value="4">4</option>
              <option value="6">6</option>
              <option value="8">8</option>
            </select></td>
        </tr>
      </table>


          <form method="post" action="">
            <table id="tadminViewReport" border="0" width="960px" cellpadding="0" cellspacing="0">
              <tr>
                <th width="15%">Username</th>
                <th width="15%">Report ID</th>
                <th width="40%">Report Title</th>
                <th width="20%">Date submitted</th>
                <th width="10%">Status</th>
              </tr>
              <tr>
                <td>username1</td>
                <td>reportID1</td>
                <td class="reportDoc">Document 1</td>
                <td>Date 1</td>
                <td><a href="admin_report_details.html">Received</a></td>
              </tr>
              <tr>
                <td>username2</td>
                <td>reportID2</td>
                <td class="reportDoc">Document 2</td>
                <td>Date 2</td>
                <td><a href="admin_report_details.html">In Queue</a></td>
              </tr>
              <tr>
                <td>username3</td>
                <td>reportID3</td>
                <td class="reportDoc">Document 3</td>
                <td>Date 3</td>
                <td><a href="admin_report_details.html">Completed</a></td>
              </tr>
              <tr>
                <td>username4</td>
                <td>reportID4</td>
                <td class="reportDoc">Document 4</td>
                <td>Date 4</td>
                <td><a href="admin_report_details.html">In Queue</a></td>
              </tr>
              <tr>
                <td>username5</td>
                <td>reportID5</td>
                <td class="reportDoc">Document 5</td>
                <td>Date 5</td>
                <td><a href="admin_report_details.html">In Queue</a></td>
              </tr>
              <开发者_如何学编程tr>
                <td>username6</td>
                <td>reportID6</td>
                <td class="reportDoc">Document 6</td>
                <td>Date 6</td>
                <td><a href="admin_report_details.html">Completed</a></td>
              </tr>
              <tr>
                <td>username7</td>
                <td>reportID7</td>
                <td class="reportDoc">Document 7</td>
                <td>Date 7</td>
                <td><a href="admin_report_details.html">Completed</a></td>
              </tr>
              <tr>
                <td>username8</td>
                <td>reportID8</td>
                <td class="reportDoc">Document 8</td>
                <td>Date 8</td>
                <td><a href="admin_report_details.html">Received</a></td>
              </tr>
              <tr>
                <td>username9</td>
                <td>reportID9</td>
                <td class="reportDoc">Document 9</td>
                <td>Date 9</td>
                <td><a href="admin_report_details.html">Received</a></td>
              </tr>
              <tr>
                <td>username10</td>
                <td>reportID10</td>
                <td class="reportDoc">Document 10</td>
                <td>Date 10</td>
                <td><a href="admin_report_details.html">Received</a></td>
              </tr>
            </table>
            <div id="pageNavPosition"></div>
            <br />
          </form>

          <script type="text/javascript"><!--
            reportsPerPage = listDisplayPerPg.options[listDisplayPerPg.selectedIndex].value;
            var pager = new Pager('tadminViewReport', reportsPerPage); 
            pager.init(); 
            pager.showPageNav('pager', 'pageNavPosition'); 
            pager.showPage(1);
        //--></script>


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

    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('pg'+this.currentPage);
        oldPageAnchor.className = 'pg-normal';

        this.currentPage = pageNumber;
        var newPageAnchor = document.getElementById('pg'+this.currentPage);
        newPageAnchor.className = 'pg-selected';

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

        var pgNext = document.getElementById(this.pagerName + 'pgNext');
        var pgPrev = document.getElementById(this.pagerName + 'pgPrev');

        if (pgNext != null) {
            if (this.currentPage == this.pages) pgNext.style.display = 'none';
            else pgNext.style.display = '';
        }
        if (pgPrev != null) {
            if (this.currentPage == 1) pgPrev.style.display = 'none';
            else pgPrev.style.display = '';
        }
    }   

    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);

        var pagerHtml = '<span id="' + pagerName + 'pgPrev" onclick="' + pagerName + '.prev();" class="pg-normal"> &#171 Prev </span> &nbsp; ';
        for (var page = 1; page <= this.pages; page++) 
            pagerHtml += '<span id="pg' + page + '" class="pg-normal" onclick="' + pagerName + '.showPage(' + page + ');">' + page + '</span> &nbsp; ';
        pagerHtml += '<span id="' + pagerName + 'pgNext" onclick="'+ pagerName+'.next();" class="pg-normal"> Next &#187;</span>';            

        element.innerHTML = pagerHtml;
    }
}

I got it works http://pastebin.com/FKpKWdMM

Basically this is the only change..

var from = (pageNumber - 1) * itemsPerPage + 1;
var to = from + itemsPerPage - 1;

change it to:

var from = (pageNumber - 1) * Number(itemsPerPage) + 1;
var to = (from + Number(itemsPerPage)) - 1;

If you don't know how to use Chrome Developers Tool / Firebug to debug javascript, I would strongly recommend you to learn that. That's one skill that is super useful!