Node 4 compatibility

Author: martinheidegger

EventProxy.js

@@ -49,11 +49,6 @@ Object.assign(EventProxy.prototype, {
     this._initEventProxy(eventName)
     return this
   },
-  prependListener: function (eventName, listener) {
-    EventEmitter.prototype.prependListener.call(this, eventName, listener)
-    this._initEventProxy(eventName)
-    return this
-  },
   removeListener: function (eventName, listener) {
     EventEmitter.prototype.removeListener.call(this, eventName, listener)
     this._exitEventProxy(eventName)
@@ -76,18 +71,29 @@ Object.assign(EventProxy.prototype, {
     }
     return this.addListener(eventName, wrapper)
   },
-  prependOnceListener: function (eventName, listener) {
-    var self = this
-    var wrapper = function (payload) {
-      listener(payload)
-      self.removeListener(eventName, wrapper)
-    }
-    return this.prependListener(eventName, wrapper)
-  },
   on: function (eventName, listener) {
     return this.addListener(eventName, listener)
   },
   off: function (eventName, listener) {
     return this.removeListener(eventName, listener)
   }
 })
+
+// Node 4 compatibility
+if (EventEmitter.prototype.prependListener) {
+  Object.assign(EventProxy.prototype, {
+    prependListener: function (eventName, listener) {
+      EventEmitter.prototype.prependListener.call(this, eventName, listener)
+      this._initEventProxy(eventName)
+      return this
+    },
+    prependOnceListener: function (eventName, listener) {
+      var self = this
+      var wrapper = function (payload) {
+        listener(payload)
+        self.removeListener(eventName, wrapper)
+      }
+      return this.prependListener(eventName, wrapper)
+    }
+  })
+}

EventProxy.test.js

@@ -36,27 +36,30 @@ tape('once', function (t) {
   t.end()
 })
 
-tape('prepend once', function (t) {
-  var target = new events.EventEmitter()
-  var proxy = new EventProxy(target)
-  var count = 0
-  target.addListener('hello', function () {
-    count += 1
-  })
-  proxy.addListener('hello', function () {
-    count += 2
-  })
-  var addResult = proxy.prependOnceListener('hello', function (data) {
-    t.equals(count, 1, 'event called once, before the listeners on proxy, after the listeners on target')
-    t.equals(data, 'world', 'data passed through')
-    count += 1
+// Node 4 compatibility
+if (events.EventEmitter.prototype.prependOnceListener) {
+  tape('prepend once', function (t) {
+    var target = new events.EventEmitter()
+    var proxy = new EventProxy(target)
+    var count = 0
+    target.addListener('hello', function () {
+      count += 1
+    })
+    proxy.addListener('hello', function () {
+      count += 2
+    })
+    var addResult = proxy.prependOnceListener('hello', function (data) {
+      t.equals(count, 1, 'event called once, before the listeners on proxy, after the listeners on target')
+      t.equals(data, 'world', 'data passed through')
+      count += 1
+    })
+    t.equals(addResult, proxy, 'Result of prepend once is proxy instance')
+    target.emit('hello', 'world')
+    target.emit('hello', 'mundo')
+    t.equals(count, 7)
+    t.end()
   })
-  t.equals(addResult, proxy, 'Result of prepend once is proxy instance')
-  target.emit('hello', 'world')
-  target.emit('hello', 'mundo')
-  t.equals(count, 7)
-  t.end()
-})
+}
 
 tape('remove all listeners', function (t) {
   var target = new events.EventEmitter()