submit form ajax (not Working)

index.html.erb

		// Reload types by AJAX POST
		$form.submit(function (event) {
			event.preventDefault();
			var data = $form.serialize();
			$.ajax({
				type:     "POST",
				url:      form_action,
				dataType: "json",
				data:     data,
				success:  function (json) {
					alert("SUCCESS");
				},
				error:    function (XMLHttpRequest, textStatus, errorThrown) {
					console.log(XMLHttpRequest);
					console.log(textStatus);
					console.log(errorThrown);
					return false;
				}
			});
		});