Right now we use codemirror's JavaScript mode on the website but there's a JSX mode now so we should start using that instead.

if (next && !isModifierKey(e)) maybeTransition = setTimeout(function() {
      if (getKeyMap(cm.options.keyMap) == startMap) {
        cm.options.keyMap = (next.call ? next.call(null, cm) : next);
        keyMapChanged(cm);
      }
    }, 50);
    var name = keyName(e, true), handled = false;
    if (!name) return false;
    var keymaps = allKeyMaps(cm);
    if (e.shiftKey) {
      
      
      
      handled = lookupKey("Shift-" + name, keymaps, function(b) {return doHandleBinding(cm, b, true);})
             || lookupKey(name, keymaps, function(b) {
                  if (typeof b == "string" ? /^go[A-Z]/.test(b) : b.motion)
                    return doHandleBinding(cm, b);
                });
    } else {
      handled = lookupKey(name, keymaps, function(b) { return doHandleBinding(cm, b); });
    }
    if (handled) {
      e_preventDefault(e);
      restartBlink(cm);
      if (ie_lt9) { e.oldKeyCode = e.keyCode; e.keyCode = 0; }
      signalLater(cm, "keyHandled", cm, name, e);
    }
    return handled;
  }
  function handleCharBinding(cm, e, ch) {