Simple form validation where inputs are checked on 'keyup' for value

simple_form_validation.php

$("form > input").keyup(function () {
    var e = !1;
    $("form > input").each(function () {
        "" == $(this).val() && (e = !0);
    }),
        e ? $("#submit").attr("disabled", "disabled") : $("#submit").removeAttr("disabled");
});