Try this:
error: function(jqXHR, textStatus, errorThrown) {
console.log(textStatus, errorThrown);
}
If you want to inform your frontend about a validation error, try to return json:
dataType: 'json',
success: function(data, textStatus, jqXHR) {
console.log(data.error);
}
Your asp script schould return:
{"error": true}