Method hook

lib/command.js:488–500

* Add hook for life cycle event. * * @param {string} event * @param {Function} listener * @return {Command} `this` command for chaining

(event, listener)

   */

  hook(event, listener) {
    const allowedValues = ['preSubcommand', 'preAction', 'postAction'];
    if (!allowedValues.includes(event)) {
      throw new Error(`Unexpected value for event passed to hook : '${event}'.
Expecting one of '${allowedValues.join("', '")}'`);
    }
    if (this._lifeCycleHooks[event]) {
      this._lifeCycleHooks[event].push(listener);
    } else {
      this._lifeCycleHooks[event] = [listener];
    }
    return this;
  }

  /**
   * Register callback to use as replacement for calling process.exit.