I'm just trying to get this checkbox to alert a message after it is checked and after it is unchecked by running a function in Javascript. I can get it to display the checked message but can't get the unchecked alert to come up.

<input type=checkbox id=chbx onchange=foo()>

<script type=text/javascript>

var checkbox = document.getElementById(chbx);



 function foo(){

   if(checkbox.checked=true){

       alert(Checked!);

         }

   else {

        alert(UnChecked!);

         }

    };

</script>