使用JavaScript后自动完成功能不起作用

Question

任何人都可以帮助我，为什么自动填充功能在首次使用后不起作用

我的代码在这里

$(document).on("keydown", "#ContentPlaceHolder1_TxtBookName", function (e) {
        if (e.which == 38) {
            var editMode = $("#ContentPlaceHolder1_hdnEdit");
            if (editMode.val() != "true") {
                var submit = $("#ContentPlaceHolder1_BtnSubmit").attr("disabled");
                var add = $("#ContentPlaceHolder1_Btnadd").attr("disabled");
                var cancel = $("#ContentPlaceHolder1_BtnCancel").attr("disabled");
                if (submit == undefined && add == "disabled" && cancel == undefined) {
                    $(ContentPlaceHolder1_txtBookCode2).val(null);
                    $(ContentPlaceHolder1_txtBookType).val(null);                        $(ContentPlaceHolder1_txtBookCode2).removeAttr("disabled");
                    $(ContentPlaceHolder1_txtBookType).attr("disabled", "disabled");
                    $(ContentPlaceHolder1_txtBookCode2).focus();
                }
            }
        }
    });