You're missing an end bracket on your final if
statement. Corrected:
/* ...snip */
window.onkeydown = function(event) {
if (event.keyCode === 81) {
addCookies();
}
if (event.keyCode === 87) {
removeCookies();
}
if (event.keyCode === 18) {
alert('To add cookies, press "Q". To remove cookies, press "W".');
}
};