From a6e21eaf4090c11d5251423089516e4742f16bc9 Mon Sep 17 00:00:00 2001
From: Dahan Gong <gdh1995@qq.com>
Date: Fri, 13 Jan 2017 19:23:37 +0800
Subject: [PATCH] allow Eventable.off to remove a group of listeners

It may do this when the argument `listener` is `undefined`.
---
 src/Eventable.js | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/Eventable.js b/src/Eventable.js
index cb3433f4d..a7976b954 100644
--- a/src/Eventable.js
+++ b/src/Eventable.js
@@ -36,11 +36,11 @@ class Eventable {
 
   on (eventType, listener) {
     // if this type of event was never bound
-    if (!(eventType in this)) {
-      this[eventType] = [listener];
+    if (this[eventType]) {
+      this[eventType].push(listener);
     }
     else {
-      this[eventType].push(listener);
+      this[eventType] = [listener];
     }
   }
 
@@ -50,7 +50,11 @@ class Eventable {
     const index     = eventList? indexOf(eventList, listener) : -1;
 
     if (index !== -1) {
-      this[eventType].splice(index, 1);
+      eventList.splice(index, 1);
+    }
+    let undef;
+    if (eventList && eventList.length === 0 || undef === listener) {
+      this[eventType] = undef;
     }
   }
 }