I've got a simple form where the user enters his contact number. If the contact number starts with 07 then the checkbox is enabled anything else I need it to be disabled.
I have written some code but the problem I face is when the user types 01 then it's disabled but if they then go on to add any other numbers after the 01 the checkbox becomes enabled.
function deselectcheckbox(wildvalue) {
  if (document.getElementById("1").value == "01") {
   $("#checkbox").attr("disabled", true);
   document.getElementById("divText").innerHTML = "Not able to send";
  }
  else
   {
   $("#checkbox").attr("disabled", false);
   document.getElementById("divText").innerHTML = "Send text";
  }
}<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<table>
<tr>
 <td>Contact Number</td>
 <td><input type="text" id="1" name="1" onkeyup="deselectcheckbox(this.value)"></td>
</tr>
<tr>
 <td><label><div id="divText">Send text</div></label></td>
 <td><input type="checkbox" name="contact" id="checkbox" value=""></td>
</tr>
</table>I've tried adding a wildcard to
(document.getElementById("1").value == "01*")
But it's not working, Please help
 
     
    