joyent/node — comment on commit 5f08c3cfa1ee3ece6032d1ffeda6f403e54dd5c0
File: lib/child_process.js line 109
By visionmedia:

wouldn't it be safe to assume `message.cmd` is a string here? (didn't look at the rest), and just use `(msg && 0 == msg.cmd.indexOf('NODE_')`