(Resolvido) Erro: has no properties

function iframe_cep() {var verifica = '57045-670';alert(verifica); if( verifica == "" ) { var cep = document.getElementById('cepDest').value; var peso = document.getElementById('pesoDeclarado').value; var cep_aux = cep.substring(0,5); } else { var cep = '57045-670'; var peso = document.getElementById('pesoDeclarado').value; var cep_aux = cep.substring(0,5); }}

e o campo é esse :

<input type="text" name="pesoDeclarado" id="pesoDeclarado" value="6.00">pq o erro document.getElementById("pesoDeclarado") has no properties ?