The nuisance of unknown JavaScript error - try and catch

<script>
bbb = function(){
      b1 = document.getElementById("jjjj").innerHTML ; 
      b1.click();
       }
</script>

<script>
 try{
     bbb()
      }catch(err)
   {
      txt="There was an error on this page.\n\n";

      txt+="Error description: " + err.message + "\n\n";

      txt+="Click OK to continue.\n\n";

      alert(txt);
    }
</script>