hotkeys - Javascript performing function if control + s are depressed -

i new javascript , want know how call function if control + s depressed on webpage. far have come :

<%    document.body.onclick = function(e){     if (e.ctrlkey){         document.body.onclick = function(f){             if(f.keycode = 115){}                 menubar.saveaction();             }         }     }      if (e.keycode = 115){         document.body.onclick = function(f){             if(f.ctrlkey){}                 menubar.saveaction();             }         }     } }  %>   

any appreciated.

like this:

document.addeventlistener("keydown", function(e) {     if(e.ctrlkey && e.keycode === 83) { // 83 = s         e.preventdefault(); // prevent default browser action         alert("ctrl + s"); // code goes here     } });