jQuery running at the same time when page loading

I need your help. I have a jquery code which is working nice after I first load the page and as a second step check the checkbox. In background function updateSg(opts) invokes the submit.php which results a Json.

But I would like to solve when I open the page, the checkbox input tag gets the checked value from URL, and the checkbox is checked but the jquery code is not run. I have to uncheck and check again for the code running.

Could you give me a help that the code is executed with the page loading together.

Thanks, Atti

<div id="result"></div>
<div id="filter">
  <h2>Filter</h2>
  <div>
    <input type="checkbox" id="sg" name="sg" checked>
    <label for="sg">Something</label>
  </div>
</div>
<script src="http://ift.tt/rs8qB8"></script> 

<script>
  var getsg = "something";

  function makeTable(data){
   var tbl_body = "";
        $.each(data, function(k,v) {
        tbl_body += getsg;
        })
    return tbl_body;
  }

  function getSgFilterOptions(){
    var opts = [];
    $checkboxes.each(function(){
      if(this.checked){
        opts.push(this.name);
      }
    });

    return opts;
  }

  function updateSg(opts){
    $.ajax({
      type: "POST",
      url: "submit.php",
      dataType : 'json',
      cache: false,
      data: {filterOpts: opts},
      success: function(records){
        $('div#result').html(makeTable(records));
      }
    });
  }

  var $checkboxes = $("input:checkbox");
  $checkboxes.on("change", function(){
    var opts = getSgFilterOptions();
    updateSg(opts);
  });

  updateSg();

  </script>