我怎样才能用js检查asp.net中“ DropDownList”的值？

Question

I'm new in asp.net and java script. i want to check value of asp:dropdownlist' with java script.

selected value define in database but when i select an item with value 9 i didn't get back "hello" alert.any body can help me ? thanks.

<script>
    $(document).ready(function offermessage() {
        var a = ($('#<%=offermessage.ClientID %> option:selected').val());
        if(a==9)
        {
            alert("hello");
        }
    });
</script>

   <div class="col-12">
       <asp:DropDownList ID="offermessage" CssClass="farsi-font drp-down-list" required="" runat="server" >
           <asp:ListItem Value="Baseid">value</asp:ListItem>
       </asp:DropDownList>
   </div>

Answer 1

can you try with the below code

 $(document).ready(function(){
            function offermessage() {
            var a = $('#<%=offermessage.ClientID%>').val();
            if(a == 9)
            {
                alert("hello");
            }
          }
        });

if you want to get the value of the dropdown on change event of dropdown then you can add below code

$(document).ready(function(){
  $('#<%=offermessage.ClientID%>').on('change',function(){
    var a = $(this).val();
      if(a == 9)
      {
       alert("hello");
      }
 });

});