Question

How do I execute a function in JavaScript when a text box is populated with text? The text box with be hidden from the user. It will be populated by a USB magnetic card swiper.

Pseudo code:

<script language="javascript" type="text/javascript">
    function MyFunction() {
        //execute this function when MyTxtBox is populated
    }
</script>
<asp:TextBox id="MyTxtBox" runat="server" Visible="false" />

Answer 1

Seems like you’re doing this when the page loads. If you are, this would work.

$(document).ready(function(){
   if($('#MyTxtBox').val().length > 0){
      MyFunction();
   }
});

If it’s on change:

$(document).ready(function(){
   $('#MyTxtBox').change(function(){
       if($(this).val().length > 0){
          MyFunction();
       }
   });
});