Given a (parent) process ID, getcpids will return an array of child process IDs.
var getcpids = require('getcpids');
var cpids = getcpids(parent.pid);
Came across a situation recently when spawning an instance of a program with pty.js, the process id was available but child process IDs of the program weren't. When the binary finished it left the child processes orphaned which can take a while to expire. Writing getcpids (which loops from 0 - 32767 calling getpgid) creates and returns an array of child process IDs which could be used to kill the orphans after the parent process ended.