Send keystroke from Javascript to Photoshop ?!

If you want to mimic the pressing of a key you can just run a vbs script or a .command on mac to send a keystroke.

if(IsWindowsOS()){
  var mb_keystrF = new File(File($.fileName).path +"/kestr.vbs");
    var str = 'WScript.Sleep 1500\
Set WshShell = WScript.CreateObject("WScript.Shell")\
WshShell.SendKeys "5"\
WScript.Sleep 1500\
WshShell.SendKeys "%g"';
    mb_keystrF.open('w');
    mb_keystrF.write(str);
    mb_keystrF.close();
  mb_keystrF.execute();
}
if(IsMacintoshOS()){
  var mb_keystrF = new File(File($.fileName).path +"/kestr.command");
    var str = 'echo\'\
delay 1.5\
tell application "Photoshop" to activate\
delay 0.1\
tell application "System Events" to keystroke "5"\
delay 0.1\
tell application "System Events" to keystroke "g" using option down\
delay 0.02\
\' | osascript';
    mb_keystrF.open('w');
    mb_keystrF.write(str);
    mb_keystrF.close();
    mb_keystrF.execute();
}


function IsMacintoshOS() {
    if ( $.os.search(/macintosh/i) != -1 ) {
        return true;
    } else {
        return false;
    }
}
function IsWindowsOS() {
    if ( $.os.search(/windows/i) != -1 ) {
        return true;
    } else {
        return false;
    }
}

There might be, but I think only some keys can be captured due to security threats of key logging. People don't want scripts that can capture what they type.