jquery shows wrong page

This is the jquery

$(document).on('change', '.ui-slider-switch', function () {
 
       if ($(this).val() == 'on') {
        $("#content1").hide();
        $("#content2").show();
 
       } else {
        $("#content1").show();
        $("#content2").hide();
        }
 
   });
 

My HTML

<div id="switch" data-role="fieldcontain">      
          <select name="slider" id="flip-a" data-role="slider">
          <option value="off"></option>
          <option value="on"></option>
          </select>  
      </div>
 

In my site I sometimes use a custom URL (And get data out of it with $ _GET).
When the page reload I'm always getting $("#content2").show(); instead of $("#content1").show();

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