jquery - Troubles getting value from bootstrap-slider -

i using bootstrap slider forecasting tool building. have following function:

function updatecontractconcern () {      showloader();      var funcid = "call_chart_contract_concern"     var forecastperiod = $('#forecastslider').data('slider').getvalue();     //var forecastperiod = 4;      console.log('forecastperiod')      var jqxhr = $.getjson('functions/getfunctions.php', {         "forecastperiod":forecastperiod,         "funcid":funcid}).done(function(datachart) {              hideloader();              if (datachart == null) {                 bootbox.alert("er geen data voor deze selectie aanwezig");             } else {                 setbasicpropertiesaveragescorechart();                 averagescorechart.dataprovider = datachart;                 averagescorechart.categoryfield = "organisatie";                 averagescorechart.validatedata();               }              })         .fail(function() { hideloader(); bootbox.alert("er kon geen data verkregen worden uit de database"); }); //when getjson request fails } 

the problem having here var forecastperiod = $('#forecastslider').data('slider').getvalue(); not give me value of slider. thoughts on this?

the html code follow:

 <div class=text-center>     <label id="labelforecastslider"><i class="fa fa-clock-o" id="iconclock"></i>  bepaal de forecast periode:</label> <!-- range -->     <input id="forecastslider" data-slider-id='forecastslider' type="text" data-slider-min="1" data-slider-max="12" data-slider-step="1" data-slider-value="0"/>  </div> 

the javascript goes slider is:

var slider = new slider("#forecastslider", {     focus: true,     formatter: function(value) {         var months = ['t/m januari', 't/m februari', 't/m maart', 't/m april', 't/m mei', 't/m juni', 't/m juli', 't/m augustus', 't/m september', 't/m oktober', 't/m november', 't/m december'];         return months[value - 1];     } }); 

when use var forecastperiod = $('#forecastslider').val();, nothing happens, when set variable "hard" number this: var forecastperiod = 2; code work.

since bootstrap-slider can seen input field, want use following code:

var forecastperiod = $('#forecastslider').val(); 

hope helps you!