EDIT

function CacheBot(pageTaxaUrl, taxonPageUrl, pageSize, progressCallback, readyCallback, doneCallback, errorCallback){

  var taxonPageUrl = taxonPageUrl;

  var pageTaxaUrl = pageTaxaUrl;

  var pageSize = null;

  var progress = 0;

  var i = 0;

  var doRun = false;

  var dataPager = null;

//  this.elapsedMillies = 0;

//  this.estimatedMillies = 0;

  /**

   * Log to the Firebug Console if Firebug is available

   * @param msg the massage to show in the firebug Console

   * @return

   */

  var log = function(msg){

    if (window.console && window.console.firebug){

      console.log(msg);

    }

  };

  /**

   *

   * @param data

   * @param statusText

   * @return

   */

  var init = function(data, statusText){

     dataPager = data;

     if(dataPager != undefined){

       progressCallback(progress, null, null, "Ready!");

     }

     if(readyCallback != undefined){

       readyCallback();

     }

     elapsedMillies = 0;

     estimatedMillies = 0;

  };

  /**

   *

   * @param callback

   * @return

   */

  var requestNextDataPage = function(callback){

    var nextPageIndex = 0;

    if(dataPager != null){

        nextPageIndex = dataPager.nextIndex;

    }

    var uriParams = (pageSize != null ? "&pageSize=" + pageSize : '');

    uriParams += "&pageNumber="+ nextPageIndex;

    log('page->' + uriParams);

    uri = pageTaxaUrl +  escape(escape(uriParams));

    jQuery.ajax({

      url: uri,

      dataType: 'json',

      cache: false, // browser will not cache

      success: callback,

      error: function(XMLHttpRequest, statusText ){

          stop();

          errorCallback(statusText, 'A network error occurred, please start again.', unescape(uri), true);

        }

    });

  };

  /**

   *

   */

  this.processNextPage = function(lastMillies){

     //

    var now = new Date();

    var nowMillies = now.getTime();

    if(lastMillies != undefined){

      elapsedMillies += (nowMillies - lastMillies);

      estimatedMillies = (elapsedMillies / i) * dataPager.count;

    }

    var thisCacheBot = this;

    // get next page of data

    if( i > dataPager.lastRecord - 1 && i < dataPager.count && dataPager.nextIndex != undefined){

      requestNextDataPage(function(data, statusText){

        if(statusText == 'success'){

          dataPager = data;

          thisCacheBot.processNextPage(nowMillies);

        } else {

          thisCacheBot.stop();

          readyCallback(statusText);

        }

      });

    } else {

      // update the progress callback

      var p = (i / dataPager.count);

      if(p != progress){

        progress = p;

        progressCallback(progress, new Date(elapsedMillies), new Date(estimatedMillies));

      }

      // get the cdm_dataportal taxon page

      if (doRun == true && i++ < dataPager.count){

        var ri = i - (dataPager.firstRecord);

        var taxon = dataPager.records[ri];

        var taxonUrl = taxonPageUrl + taxon.uuid + '/all';

        log('taxon->'+taxonUrl);

        jQuery.ajax({

          url: taxonUrl,

          cache: false, // browser will not cache

          complete: function(xmlHttpRequest, statusText){

              if(xmlHttpRequest.status != 200){

                errorCallback(statusText, null, unescape(taxonUrl), false);

              }

              thisCacheBot.processNextPage(nowMillies);

            }

        });

        taxon = null;

      } else if(i == dataPager.count) {

        // DONE!

        if(doneCallback != undefined){

          doneCallback();

         }

      } else if(doRun == false){

        readyCallback();

      }

    }

  };

  /**

   *

   */

  this.start =  function(){

      doRun = true;

      this.processNextPage();

    };

  /**

   *

   */

    this.stop = function(){

      doRun = false;

    };

  // get list of taxa and initialize the Bot

  progressCallback(0, null, null, "Initializing, please wait ...");

  requestNextDataPage(function(data, statusText){

    init(data, statusText);

  });

}

// -----------------------------------------------------------------------------

jQuery(document).ready(function($) {

  var pageTaxaUrl = $('#cdm-settings-cache [name=pageTaxaUrl]').val();

  var taxonPageUrl = $('#cdm-settings-cache [name=taxonPageUrl]').val();

  $('#cdm-settings-cache [name=start]').attr('disabled', 'disabled');

  $('#cdm-settings-cache [name=stop]').attr('disabled', 'disabled');

  $('#cdm-settings-cache #progress').css({background: '#012456', color: '#349AAF', fontSize: '100%', padding: '10px'});

  $('#cdm-settings-cache #progress').html(

        '<div id="usermessage" style="font-size:95%; width: 50%; float:right; font-weight:light; padding:10px; border-left: 1px solid; height: 3.9em;"></div>'

        +'<div id="counter" style="font-size:300%; padding:10px;"></div>'

        +'<div id="time" style="clear:both; border-top:1px solid #349AAF;"></div>'

        +'<div id="log" style="border-top:1px solid #349AAF; font-size:85%; overflow: auto; white-space:nowrap;"></div>');

  var formatTime = function(date){

    var h = parseInt(date.getTime() / 1000 / 60 / 60);

    var m = parseInt( (date.getTime() / 1000/ 60) % 60);

    var s = parseInt( (date.getTime() / 1000 ) % 60);

    return '' + h +'h '+ m +'m '+ s +'s ';

  };

  var progressCallback = function(progress, elapsedTime, estimatedTime, userMessage){

    var percent = Math.floor(progress * 10000) / 100;

    $('#counter').text(percent + '%');

    if(elapsedTime != null){

      var timehtml =

        'elapsed time: ' + formatTime(elapsedTime)

        + '<br />estimated time: ' + formatTime(estimatedTime)

        + '<br />remaining time: ' + formatTime(new Date(estimatedTime.getTime() - elapsedTime.getTime()));

      $('#time').html(timehtml);

    }

    if(userMessage == undefined || userMessage == null ){

      userMessage = '';

    }

    $('#usermessage').html(userMessage);

  };

  var readyCallback = function(message){

    $('#cdm-settings-cache [name=start]').removeAttr('disabled');

    if(message != undefined){

      $('#cdm-settings-cache').append('<div class="error">'+message+'</div>');

    }

  };

  var doneCallback = function(progress){

    $('#cdm-settings-cache #progress').text('DONE');

    $('#cdm-settings-cache [name=stop]').removeAttr('disabled');

  };

  var errorCallback = function(errorMessage, userMessage, taxonUrl, doStop){

    var logentry = '<div>' + errorMessage + ' : ' + taxonUrl + '' + '</div>';

    if($('#log div').length == 0){

      $('#log').html(logentry);

    } else {

      $('#log div:last').append(logentry);

    }

    if(userMessage == undefined || userMessage == null ){

      userMessage = '';

    }

    $('#usermessage').html(userMessage);

    if(doStop){

      $('#cdm-settings-cache [name=stop]').attr('disabled', 'disabled');

      $('#cdm-settings-cache [name=start]').removeAttr('disabled');

    }

  };

  var cacheBot = new CacheBot(pageTaxaUrl, taxonPageUrl, 25, progressCallback, readyCallback, doneCallback, errorCallback);

  $('#cdm-settings-cache [name=start]').click(function(){

    cacheBot.start();

    $('#cdm-settings-cache [name=start]').attr('disabled', 'disabled');

    $('#cdm-settings-cache [name=stop]').removeAttr('disabled');

    $('#usermessage').html(' ');

  }).attr('disabled', 'disabled');

  $('#cdm-settings-cache [name=stop]').click(function(){

    cacheBot.stop();

    $('#cdm-settings-cache [name=stop]').attr('disabled', 'disabled');

  }).attr('disabled', 'disabled');

});