Nodejs snippet to handle `process` events (OS signals) easily with `addSignalListener()`

addSignalListener.mjs

/**
 * Handle process signal events easily with `addSignalListener()`.
 * 
 * Automatically returns a convenient method to unregister your event handler(s), in case you need that functionality.
 *
 * ## Examples
 * 
 * ```js
 * addSignalListener(['SIGINT', 'SIGHUP', 'SIGUSR2'], (signal, event) =>
 *   console.log(`Process received a signal! ${signal}`, { event });
 * );
 *
 * const removeListener = addSignalListener('SIGINT', (signal) => console.log(`App Interrupted!`));
 * removeListener();
 * 
 * addSignalListener(['unhandledRejection', 'uncaughtException'], console.error);
 *
 * // Specify signals as object keys, where values are ignored and can be used as comments.
 * addSignalListener({
 *     SIGHUP: 1,
 *     SIGINT: 2,
 *     SIGUSR2: 15,
 *   }, (signal, event) => {
 *     client.close();
 *     db.close();
 *     console.log(`Process received a signal! ${signal}`, { event });
 *   },
 *   true);
 * ```
 *
 * Returns a cleanup function to remove the listeners that were added.
 * @param {number | string | object | number[] | string[] } signals
 * @param {function} handler callback 
 * @param {boolean} onlyOnce default is `false`
 *
 */
export const addSignalListener = (
  signals,
  handler,
  onlyOnce,
) => {
  signals =
    signals && isPrimitive(signals)
      ? [signals]
      : Array.isArray(signals)
      ? signals
      : typeof signals === 'object'
      ? Object.keys(signals)
      : [];

  const signalHandlers = {};

  signals.forEach((signal) => {
    signalHandlers[signal] = (...args) => handler(signal, ...args);
    process[onlyOnce ? 'once' : 'on'](signal, signalHandlers[signal]);
  });

  // Return a cancel function that will remove the listeners
  return () =>
    signals.forEach((signal) => process.off(signal, signalHandlers[signal]));
};

const isPrimitive = (value) =>
  typeof value === 'string' ||
  typeof value === 'number' ||
  typeof value === 'boolean' ||
  typeof value === 'symbol' ||
  typeof value === 'undefined' ||
  value === null;