From c8e941cff707fadaa2773a0c48a824b58159378e Mon Sep 17 00:00:00 2001
From: Sceat <sceat@hydre.io>
Date: Tue, 5 May 2020 22:11:48 +0200
Subject: [PATCH] supporting custom events

---
 lib/event-target.js | 44 ++++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/lib/event-target.js b/lib/event-target.js
index a294b37a3..edac08e63 100644
--- a/lib/event-target.js
+++ b/lib/event-target.js
@@ -111,47 +111,51 @@ const EventTarget = {
    *
    * @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
+   * @param {Object} [options] An options object specifies characteristics
+   * about the event listener
    * @public
    */
   addEventListener(method, listener, options = {}) {
     if (typeof listener !== 'function') return;
-    const { once } = options;
 
     function onMessage(data) {
       listener.call(this, new MessageEvent(data, this));
-      if(once) this.removeListener(method, listener);
     }
 
     function onClose(code, message) {
       listener.call(this, new CloseEvent(code, message, this));
-      if(once) this.removeListener(method, listener);
     }
 
     function onError(error) {
       listener.call(this, new ErrorEvent(error, this));
-      if(once) this.removeListener(method, listener);
     }
 
     function onOpen() {
       listener.call(this, new OpenEvent(this));
-      if(once) this.removeListener(method, listener);
     }
 
-    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);
+    const type = options.once ? 'once' : 'on';
+
+    switch (method) {
+      case 'message':
+        onMessage._listener = listener;
+        this[type](method, onMessage);
+        break;
+      case 'close':
+        onClose._listener = listener;
+        this[type](method, onClose);
+        break;
+      case 'error':
+        onError._listener = listener;
+        this[type](method, onError);
+        break;
+      case 'open':
+        onOpen._listener = listener;
+        this[type](method, onOpen);
+        break;
+      default:
+        this[type](method, listener);
+        break;
     }
   },