event-target.js

'use strict';

/**
 * Class representing an event.
 *
 * @private
 */
class Event {
  /**
   * Create a new `Event`.
   *
   * @param {String} type The name of the event
   * @param {Object} target A reference to the target to which the event was dispatched
   */
  constructor(type, target) {
    this.target = target;
    this.type = type;
  }
}

/**
 * Class representing a message event.
 *
 * @extends Event
 * @private
 */
class MessageEvent extends Event {
  /**
   * Create a new `MessageEvent`.
   *
   * @param {(String|Buffer|ArrayBuffer|Buffer[])} data The received data
   * @param {WebSocket} target A reference to the target to which the event was dispatched
   */
  constructor(data, target) {
    super('message', target);

    this.data = data;
  }
}

/**
 * Class representing a close event.
 *
 * @extends Event
 * @private
 */
class CloseEvent extends Event {
  /**
   * Create a new `CloseEvent`.
   *
   * @param {Number} code The status code explaining why the connection is being closed
   * @param {String} reason A human-readable string explaining why the connection is closing
   * @param {WebSocket} target A reference to the target to which the event was dispatched
   */
  constructor(code, reason, target) {
    super('close', target);

    this.wasClean = target._closeFrameReceived && target._closeFrameSent;
    this.reason = reason;
    this.code = code;
  }
}

/**
 * Class representing an open event.
 *
 * @extends Event
 * @private
 */
class OpenEvent extends Event {
  /**
   * Create a new `OpenEvent`.
   *
   * @param {WebSocket} target A reference to the target to which the event was dispatched
   */
  constructor(target) {
    super('open', target);
  }
}

/**
 * Class representing an error event.
 *
 * @extends Event
 * @private
 */
class ErrorEvent extends Event {
  /**
   * Create a new `ErrorEvent`.
   *
   * @param {Object} error The error that generated this event
   * @param {WebSocket} target A reference to the target to which the event was dispatched
   */
  constructor(error, target) {
    super('error', target);

    this.message = error.message;
    this.error = error;
  }
}

/**
 * This provides methods for emulating the `EventTarget` interface. It's not
 * meant to be used directly.
 *
 * @mixin
 */
const EventTarget = {
  /**
   * Register an event listener.
   *
   * @param {String} method A string representing the event type to listen for
   * @param {Function} listener The listener to add
   * @param {Object} [options] An options object specifies characteristics about the event listener
   * @public
   */
  addEventListener(method, listener, options = {}) {
    if (typeof listener !== 'function') return;

    function onMessage(data) {
      listener.call(this, new MessageEvent(data, this));
      if (options.once) this.removeListener(method, listener);
    }

    function onClose(code, message) {
      listener.call(this, new CloseEvent(code, message, this));
    }

    function onError(error) {
      listener.call(this, new ErrorEvent(error, this));
    }

    function onOpen() {
      listener.call(this, new OpenEvent(this));
    }

    if (method === 'message') {
      onMessage._listener = listener;
      this.on(method, onMessage);
    } else if (method === 'close') {
      onClose._listener = listener;
      this.on(method, onClose);
    } else if (method === 'error') {
      onError._listener = listener;
      this.on(method, onError);
    } else if (method === 'open') {
      onOpen._listener = listener;
      this.on(method, onOpen);
    } else {
      this.on(method, listener);
    }
  },

  /**
   * Remove an event listener.
   *
   * @param {String} method A string representing the event type to remove
   * @param {Function} listener The listener to remove
   * @public
   */
  removeEventListener(method, listener) {
    const listeners = this.listeners(method);

    for (let i = 0; i < listeners.length; i++) {
      if (listeners[i] === listener || listeners[i]._listener === listener) {
        this.removeListener(method, listeners[i]);
      }
    }
  }
};

module.exports = EventTarget;