Simple Node forever code

forever.js

#!/usr/bin/env node
const spawn = require('child_process').spawn;

const cmd = process.argv.shift(); // node cmd path
const args = ['./bin/www'];

// server starter is exit then exit all
let ps = null;
function killChildProcess() {
  if (ps) {
    ps.kill();
    ps = null;
  }
}

process.on('exit', function() {
  console.log('Server starter exit');
  if (ps) ps.kill();
});
process.on('SIGINT', function() {
  process.exit();
});

(function main() {
  console.log(`Sever starter pid: ${process.pid}`);
  console.log(`Sever start command: ${cmd} ${args.toString()}`);

  killChildProcess();
  ps = spawn(cmd, args, {
    cwd: process.cwd(),
    detached: true,
    stdio: 'inherit',
  });
  console.log(`Server pid: ${ps.pid}`);

  // server forever start!
  ps.on('exit', function() {
    console.log('Server exit by unknown problem, retry server start');
    killChildProcess();
    setTimeout(main, 1000);
  });
})();