Question

On my page, I’m using textbox with calendar extender to get the date value.
I’ve added onchange="ValidateStartDate();" to the textbox.

 <asp:TextBox ID="TextBoxStartDate" runat="server"  ForeColor="Red"    
     onchange="ValidateRsmStartDate();"> 
     </asp:TextBox>               

<asp:CalendarExtender ID="CalendarExtenderStartDate" 
  TargetControlID="TextBoxStartDate"
  BehaviorID="ceStartDate"  
  PopupButtonID="CalendarExtenderStartDatePopup"                                                                     
  Format="MM/dd/yyyy" runat="server">
  </asp:CalendarExtender>

<img class="Spacer" id="CalendarExtenderStartDatePopup" src="Images/Calendar.png"                                                                                
   alt="Start Date" />

My javascript function:

function ValidateStartDate() {
   var txtDate = document.getElementById('<%=TextBoxStartDate.ClientID  %>');
   alert(txtDate.innerHTML);
}

But on alert(), I get no value at all.

Answer 1

Textbox does not have innerHTML, you need to use value

Change

alert(txtDate.innerHTML);

To

alert(txtDate.value);