javascript - event.preventDefault behaving weirdly in Firefox on keydown -

The code below is effective in preventing browser defaults by firing in Chrome and Safari. For some reasons, however, my code does not run even after pressing the arrow key in Firefox

  $ (window) .keydown (function (e) {switch (e.which) {case 39: // right arrow key e.preventDefault (); $ ('body') ScrollLeft (scrollNow + z (10); break; Case 37: // left arrow key e.preventDefault (); $ ('body' ScrollLeft (scrollNow - z (10)); break;}});   
 I tried  return false; Instead of   e.preventDefault ();  Also, but I have no effect in  e.preventDefault (); Also tried to put  after the  scrollLeft  line, but is it not working either any ideas?   
 
 
 try this -  
  code = e.keyCode || E.which; Switch (code) {