// ---------------------------------------------------------------------------
// Autor: Francisco Cárdenas
// ---------------------------------------------------------------------------
function is_email(string) {
  var regexp = /^[0-9a-z\-\_]+(.[0-9a-z\-\_]+)*@[0-9a-z\-]+(.[0-9a-z\-]+)*\.[0-9a-z][0-9a-z]+$/;
  return regexp.test(string);
}
// ---------------------------------------------------------------------------