Can't get the RadSearchBox text by javascript

Question

<script type="text/javascript">            
        function getItem() {
        var sku = document.getElementById('<%=RadSearchBox1.ClientID%>').value; // Return undefind
        document.getElementById('<%= Label1.ClientID %>').innerHTML = sku;
        } 
</script>

it always return Undefined in Label1

<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" OnClientClick="getItem();return false;" />
    <asp:Label ID="Label1" runat="server" ></asp:Label>

Answer 1

You can get the input value using the code like this:

<script type="text/javascript">            
        function getItem() {
        var sku = document.getElementById('<%=RadSearchBox1.ClientID%>_Input').value; 
        document.getElementById('<%= Label1.ClientID %>').innerHTML = sku;
        } 
</script>

Notice I added _Input in document.getElementById as the search textbox id is different from RadSearchBox control