tests/minimal_runtime_exit_handling.js

function onerror(e) {
  // MINIMAL_RUNTIME + EXIT_RUNTIME throws `exit(status)` when exit() is called
  // or when main is done.
  // Unlike the normal runtime it doesn't call process.exit.
  var message = e.message || e;
  var offset = message.indexOf('exit(');
  if (offset != -1) {
    var status = message.substring(offset + 5);
    offset = status.indexOf(')')
    status = status.substr(0, offset)
    process['exitCode'] = status;
  } else {
    console.log(e)
    process['exitCode'] = 1;
  }
}

// Unhandled rejections end up here too because we run node with --unhandled-rejections=throw
process.on('uncaughtException', function(err, origin) { onerror(err); });