How to disable asp.net control in client side using javascript

Question

I want to disable Asp.net textbox on the client side using javascript if it's not empty.

I am using the following function for empty check and to disable the textbox.

<script>    
   function check(textBox) {
     if (textBox.innerText = (field.value === "")) { 
         textBox.disabled = true; 
     } 
   }    
</script>

and the following code which I used in pageload

ASPxTextBox1.Attributes.Add("onchange", "check(this);");

and following is my aspx.

  <dx:ASPxTextBox ID="ASPxTextBox1" runat="server" Height="35px" Width="44px">
          <ClientSideEvents TextChanged="function check(textBox)" />
  </dx:ASPxTextBox>

It's not working for me. I don't know what's the problem.
Is there any way to achieve the same.

Note: I am using DevExpress ASPxTextBox controls.

Answer 1

The whole function looks like as below.

 <script type="text/javascript">

    function OnTextChangedHandler(s) {
         alert('TextChanged. Text = ' + s.GetText());

         s.SetEnabled(false);
    }
</script>

Your html is as bellow.

<dx:ASPxTextBox ID="ASPxTextBox1" ClientInstanceName="txtReceiver" runat="server" Height="35px" Width="44px">
    <ClientSideEvents
        TextChanged="function(s, e) {
            OnTextChangedHandler(s);
        }" />
</dx:ASPxTextBox>

Since this is a ASPxTextBox according to their documentation s.SetEnabled(false); this code can be used to disable the control. s.GetText() can be used to get the text value from the control. For more info check this link .