javascript - detect ctrl key pressed or up, keypress event doesn't trigger -

i see similar questions here (like javascript: check if ctrl button pressed) problem event triggering. js code:

    // listen keyboard.      window.onkeypress = listentothekey;     window.onkeyup = listentokeyup;      /*         gets key pressed , send request associated function         @input key     */     function listentothekey(e)     {         if (editflag == 0)         {             // if delete key pressed calls delete             if (e.keycode == 46)                 deletenode();              // if insert key pressed calls add blank             if (e.keycode == 45)                 createblank();              if (e.keycode == 17)                 ctrlflag = 1;         }     } 

the event triggers other keys except ctrl.
need trigger ctrl.
can't use jquery/prototype/whatever solutions not acceptable.

so... how can detect ctrl?

try using if (e.ctrlkey).

mdn: event.ctrlkey