From aa2e57acc7a5e7c8642cb70c8862785ddfc220ca Mon Sep 17 00:00:00 2001
From: Ben Ripkens <bripkens.dev@gmail.com>
Date: Fri, 29 Jan 2016 11:14:04 +0100
Subject: [PATCH] Avoid memory leaks by remove event arrays

When subscribing and then unsubscribing from many different types of events,
it can be observed that the `Emitter._callbacks` object starts to grow.
This happens because, when unsubscribing, the event specific event array
is not removed when the last subscriber unsubscribes.
---
 index.js        |  7 +++++++
 test/emitter.js | 26 ++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/index.js b/index.js
index 1c78176..cb6a30a 100644
--- a/index.js
+++ b/index.js
@@ -109,6 +109,13 @@ Emitter.prototype.removeEventListener = function(event, fn){
       break;
     }
   }
+
+  // Remove event specific arrays for event types that no
+  // one is subscribed for to avoid memory leak.
+  if (callbacks.length === 0) {
+    delete this._callbacks['$' + event];
+  }
+
   return this;
 };
 
diff --git a/test/emitter.js b/test/emitter.js
index 02c3a0b..a1f1dda 100644
--- a/test/emitter.js
+++ b/test/emitter.js
@@ -142,6 +142,32 @@ describe('Emitter', function(){
 
       calls.should.eql([]);
     })
+
+    it('should remove event array to avoid memory leak', function() {
+      var emitter = new Emitter;
+      var calls = [];
+
+      function cb() {}
+
+      emitter.on('foo', cb);
+      emitter.off('foo', cb);
+
+      emitter._callbacks.should.not.have.property('$foo');
+    })
+
+    it('should only remove the event array when the last subscriber unsubscribes', function() {
+      var emitter = new Emitter;
+      var calls = [];
+
+      function cb1() {}
+      function cb2() {}
+
+      emitter.on('foo', cb1);
+      emitter.on('foo', cb2);
+      emitter.off('foo', cb1);
+
+      emitter._callbacks.should.have.property('$foo');
+    })
   })
 
   describe('.off()', function(){