使用 jQuery 在下拉列表中选择特定选定值时启用标签可见性？

Question

我正在尝试做到这一点，当用户选择某个项目时，它通过将标签的可见属性设置为 "true" 来为用户提供一些信息，它应该相对简单但我似乎无法让它发挥作用。我正在使用 Web 表单。

Aspx 代码：

<label for="footerPlaceHolder_twoFactorAuthentication" class="sr-only"><asp:Localize runat="server" Text="<%$ Resources:UserMessages, SelectTwoFactor %>"></asp:Localize></label>
                    <asp:DropDownList runat="server" ID="twoFactorAuthenticationDropDownList"  OnSelectedIndexChange="twoFactorAuthenticationDropDownList_SelectedIndex" CssClass="selectpicker">
                        <asp:ListItem Value="0" Text = "<%$ Resources:UserMessages, SelectTwoFactor %>"></asp:ListItem>
                        <asp:ListItem Value="1" Text = "<%$ Resources:UserMessages, RequireTwoFactor %>" ></asp:ListItem>
                        <asp:ListItem Value="2" Text = "<%$ Resources:UserMessages, RecommendTwoFactor %>" ></asp:ListItem>
                        <asp:ListItem Value="3" Text = "<%$ Resources:UserMessages, TwoFactorNotRequired %>" ></asp:ListItem>
                         </asp:DropDownList>
                    <p><asp:RequiredFieldValidator runat="server" ControlToValidate="paymentDay" CssClass="field-validation-error" ErrorMessage="<%$ Resources:ErrorMessages, ValidationPaymentDayRequired %>" InitialValue="0" EnableClientScript="true" Display="Dynamic"></asp:RequiredFieldValidator></p>

<h3><asp:Localize runat="server" ID="noticeLabel" Visible="false" Text="<%$ Resources:UserMessages, Notice %>"></asp:Localize></h3>
                    <h5 class="leftspace"><asp:Localize runat="server" ID="noticeText" Visible="false" Text="<%$ Resources:UserMessages, NoticeInfo %>"></asp:Localize></h5>

我尝试过的：

$(function(){
    if($("#twoFactorAuthenticationDropDownList").val() == 3)
        $("#noticeText").visible("true");
    });

Answer 1

试试这个

$(function(){
    if($("#twoFactorAuthenticationDropDownList :selected").val() === '3') {
        $("#noticeinfo").visible("true");
    }
});

Answer 2

aspx代码：

<label for="footerPlaceHolder_twoFactorAuthentication" class="sr-only"><asp:Localize runat="server" Text="<%$ Resources:UserMessages, TwoFactorSelect %>"></asp:Localize></label>
                <asp:DropDownList runat="server" ID="twoFactorAuthenticationDropDownList" CssClass="selectpicker" AppendDataBoundItems="True">
                    <asp:ListItem Value="0" Text = "<%$ Resources:UserMessages, TwoFactorSelect %>"></asp:ListItem>
                    <asp:ListItem Value="1" Text = "<%$ Resources:UserMessages, TwoFactorRequire %>" ></asp:ListItem>
                    <asp:ListItem Value="2" Text = "<%$ Resources:UserMessages, TwoFactorRecommend %>" ></asp:ListItem>
                    <asp:ListItem Value="3" Text = "<%$ Resources:UserMessages, TwoFactorNotRequired %>" ></asp:ListItem>
                     </asp:DropDownList>
                <p><asp:RequiredFieldValidator runat="server" ControlToValidate="twoFactorAuthenticationDropDownList" CssClass="field-validation-error"  InitialValue="3" EnableClientScript="true" Display="Dynamic"></asp:RequiredFieldValidator></p>

                <span ID="noticeinfo" class="leftspace"><asp:Localize runat="server"  ID="noticeText" Text="<%$ Resources:UserMessages, NoticeInfo %>"></asp:Localize></span>
                <asp:HiddenField runat="server" Value="<%$ Resources:UserMessages, twofactorMessage0 %>" ID="twofactorMessage0" />
                <asp:HiddenField runat="server" Value="<%$ Resources:UserMessages, twofactorMessage1 %>" ID="twofactorMessage1" />
                <asp:HiddenField runat="server" Value="<%$ Resources:UserMessages, twofactorMessage2 %>" ID="twofactorMessage2" />
                <asp:HiddenField runat="server" Value="<%$ Resources:UserMessages, twofactorMessage3 %>" ID="twofactorMessage3" />

正在工作的 js。代码：

$('#footerPlaceHolder_twoFactorAuthenticationDropDownList').on('change', function (e) {
        var selectedValue = $('#footerPlaceHolder_twoFactorAuthenticationDropDownList').val();
        console.log("Value of dropdown is: " + selectedValue);

    $('#noticeinfo').text($('#footerPlaceHolder_twofactorMessage' + selectedValue).val());

使用 jQuery 在下拉列表中选择特定选定值时启用标签可见性？

Enable visibility of label when a certain selected value is selected in a drop down list using jQuery?

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