How to dismiss a web modal dialog from bootstrap manually?

I have a small form dialog. the user enters a name, if the name exists or is empty an error is thrown in the dialog box. Other wise the name is added a a database and the dialog should close. The last part is what I don't know how to do it.

The breakdown is as follows:

Here is the code from the dialog (html+bootstrap).

  <div class="modal fade" id="modal_new_project" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
<div class="modal-dialog">
  <div class="modal-content">
    <div class="modal-header">
      <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>
      <h4 class="modal-title" id="myModalLabel">Nuevo proyecto</h4>
    </div>
      <div class="modal-body">
        <form action="" method="post" name="newprojform" class="form">
          <div class="form-group">
        <label for="projname" class="control-label col-xs-4">Nombre</label>
          <input type="text" class="form-control" id="projname" name="projname">
          <h3><label id="projname_status" class="label label-danger"></label></h3>
          </div>              
          <button type="button" name="verifyproject" class="btn btn-primary" onclick="errorInProyect('apretado')">Crear nuevo proyecto</button>       
        </form>
      </div>
    <div class="modal-footer">        
    </div>
  </div>
</div>
  </div> 

This calls the javascript function:

  <script>
function errorInProyect(err){
    if (document.getElementById("projname").value == ""){
      document.getElementById("projname_status").innerHTML =  "El nombre del proyecto no puede estar vacio";
    }
    else{
    var pname = document.getElementById("projname").value;
    jQuery.ajax({
        type: "POST",
        url: 'addproject.php',
        dataType: 'json',
        data: {functionname: 'check_for_existing_project', args: [pname]},
        success: function (obj) {
              if (obj.error != ""){
                document.getElementById("projname_status").innerHTML = obj.error;
              }
              else{
                //CLOSE DIALOG
              }
            }
    });
    }
}
  </script>

I need to know how to dismiss the dialog in case there were no problems