function ltrim(s) {
  return s.replace(/^\s+/, "");
}
function rtrim(s) {
  return s.replace(/\s+$/, "");
}
function trim(s) {
  return rtrim(ltrim(s));
}
function validarTexto(texto) {
  var ok = true;
  var caracter;
  var lonTexto = texto.length;
  for (i = 0; i < lonTexto; i++) {
    caracter = texto.charAt(i);
    var lonLetrasOK = letrasOK.length;
    for (j = 0; j < lonLetrasOK; j++) {
      if (caracter == letrasOK.charAt(j)) {
        break;
      }
    }
     if (j == lonLetrasOK) {
      ok = false;
      break;
    }
  }
  if (!ok) {
    return false;
  }
  else {
    return true;
  }
}
function permitirSoloNumeros(evt) {
  // NOTE: Backspace = 8, Enter = 13, '0' = 48, '9' = 57
  var key = nav4 ? evt.which : evt.keyCode;
  return (key <= 13 || (key >= 48 && key <= 57));
}
function validarMail(mail) {
  var filtro = /^[A-Za-z][A-Za-z0-9_]*@[A-Za-z0-9_]+\.[A-Za-z0-9_.]+[A-za-z]$/;
  if (filtro.test(mail)) return true; return false;
}