Alert não funciona

  var nm_form    = document.getElementById("form_cadrequerimento");
  var qtd_inputs = nm_form.elements.length;
  var campos_vazios = "";
  for (cont=0; cont<=qtd_inputs; cont++) {
    if(nm_form.elements[cont].id.substr(-2) == "_R" && $(nm_form.elements[cont]).val() == ""){
      campos_vazios = nm_form.elements[cont].id;
      alert(campos_vazios);
    }

  }
  alert('bla bla bla');