-

~ ❯❯❯ cat <<EOF | jade -O '{ nick: "chargen_" }'
script(type='text/javascript').
    window.nick = !{JSON.stringify(nick)};
EOF
<script type="text/javascript">window.nick = "chargen_";</script>%

~ ❯❯❯ cat <<EOF | jade -O '{ nick: null }'
script(type='text/javascript').
    window.nick = !{JSON.stringify(nick)};
EOF
<script type="text/javascript">window.nick = null;</script>%