EventManager.js

export class EventManager {
  constructor () {
    /**
     * @type {{ [name:string]: Array<Function> }}
     */
    this.events = {}
  }

  /**
   * @param {string} name
   * @param {Function} middleware
   */
  on (name, middleware) {
    if (typeof middleware !== 'function') {
      throw new Error('middleware requires an function')
    }
    if (!this.events.hasOwnProperty(name)) {
      this.events[ name ] = []
    }
    this.events[ name ].push(middleware)
  }

  /**
   * @param {string} name
   * @param {...any} values
   */
  emit (name, ...values) {
    if (!this.events.hasOwnProperty(name)) {
      return undefined
    }
    this.events[name].forEach(middleware => middleware(...values))
  }
}