/usr/share/proton-0.14.0/examples/javascript/messenger/ is in libqpid-proton8-dev-examples 0.14.0-5.1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/proton-0.14.0/examples/javascript/messenger/client.js
/usr/share/proton-0.14.0/examples/javascript/messenger/drain.js
/usr/share/proton-0.14.0/examples/javascript/messenger/proxy.js
/usr/share/proton-0.14.0/examples/javascript/messenger/qpid-config.js
/usr/share/proton-0.14.0/examples/javascript/messenger/recv.js
/usr/share/proton-0.14.0/examples/javascript/messenger/send.html
/usr/share/proton-0.14.0/examples/javascript/messenger/send.js
/usr/share/proton-0.14.0/examples/javascript/messenger/server.js
/usr/share/proton-0.14.0/examples/javascript/messenger/spout.js
/usr/share/proton-0.14.0/examples/javascript/messenger/ws2tcp.js