code: function broadcast (subscriptions, type) {
    return value => {
      subscriptions.forEach(s => {
        if (typeof s.emit[type] === 'function') {
          s.emit[type](value)
        }
      })
    }
  }
docs: Creates a callback function that emits values to a list of subscribers.
  
  @private
  @param {Array} subscriptions An array of subscriptions.
  @param {String} type The type of callback to create.
  @returns {Function} A function that emits a value to all of the subscriptions.