Validate ASP.Net CheckBoxList and TextBox based on condition using JavaScript

Hi Thuyai,

Check this example. Now please take its reference and correct your code.

HTML

Select Fruits<br />
<asp:CheckBoxList ID="chkFruits" runat="server">
    <asp:ListItem Text="Mango" />
    <asp:ListItem Text="Apple" />
    <asp:ListItem Text="Banana" />
    <asp:ListItem Text="Pineapple" />
    <asp:ListItem Text="Guava" />
    <asp:ListItem Text="Grapes" />
    <asp:ListItem Text="Papaya" />
    <asp:ListItem Text="Other" />
</asp:CheckBoxList>
<asp:CustomValidator ID="CustomValidator1" ErrorMessage="Please select at least one item."
    ForeColor="Red" ClientValidationFunction="ValidateCheckBoxList" runat="server" />
<br />
<asp:TextBox ID="txtOtherfruit" Rows="5" TextMode="multiline" runat="server" />
<asp:RequiredFieldValidator ID="rfvOtherFruit" ErrorMessage="Required" ControlToValidate="txtOtherfruit"
    Enabled="false" runat="server" ForeColor="Red" />
<br />
<br />
<asp:Button ID="btnSubmit" Text="Submit" runat="server" /><br />
<script type="text/javascript">
    function ValidateCheckBoxList(sender, args) {
        var checkBoxList = document.getElementById("<%=chkFruits.ClientID %>");
        var checkboxes = checkBoxList.getElementsByTagName("input");
        var isValid = false;
        for (var i = 0; i < checkboxes.length; i++) {
            if (checkboxes[i].checked) {
                isValid = true;
                if (checkboxes[i].value == 'Other') {
                    ValidatorEnable(document.getElementById("rfvOtherFruit"), true);
                    break;
                }
                break;
            }
        }
        args.IsValid = isValid;
    }
</script>

Screenshot