Consolidate listener checks

events.js

@@ -66,6 +66,12 @@ EventEmitter.prototype._maxListeners = undefined;
 // added to it. This is a useful default which helps finding memory leaks.
 var defaultMaxListeners = 10;
 
+function checkListener(listener) {
+  if (typeof listener !== 'function') {
+    throw new TypeError('The "listener" argument must be of type Function. Received type ' + typeof listener);
+  }
+}
+
 Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
   enumerable: true,
   get: function() {
@@ -159,9 +165,7 @@ function _addListener(target, type, listener, prepend) {
   var events;
   var existing;
 
-  if (typeof listener !== 'function') {
-    throw new TypeError('The "listener" argument must be of type Function. Received type ' + typeof listener);
-  }
+  checkListener(listener);
 
   events = target._events;
   if (events === undefined) {
@@ -248,18 +252,14 @@ function _onceWrap(target, type, listener) {
 }
 
 EventEmitter.prototype.once = function once(type, listener) {
-  if (typeof listener !== 'function') {
-    throw new TypeError('The "listener" argument must be of type Function. Received type ' + typeof listener);
-  }
+  checkListener(listener);
   this.on(type, _onceWrap(this, type, listener));
   return this;
 };
 
 EventEmitter.prototype.prependOnceListener =
     function prependOnceListener(type, listener) {
-      if (typeof listener !== 'function') {
-        throw new TypeError('The "listener" argument must be of type Function. Received type ' + typeof listener);
-      }
+      checkListener(listener);
       this.prependListener(type, _onceWrap(this, type, listener));
       return this;
     };
@@ -269,9 +269,7 @@ EventEmitter.prototype.removeListener =
     function removeListener(type, listener) {
       var list, events, position, i, originalListener;
 
-      if (typeof listener !== 'function') {
-        throw new TypeError('The "listener" argument must be of type Function. Received type ' + typeof listener);
-      }
+      checkListener(listener);
 
       events = this._events;
       if (events === undefined)