Add rawListeners method from Node 9.4 (#46)

Ref:
nodejs/node@decab71

events.js

@@ -428,24 +428,28 @@ EventEmitter.prototype.removeAllListeners =
       return this;
     };
 
-EventEmitter.prototype.listeners = function listeners(type) {
-  var evlistener;
-  var ret;
-  var events = this._events;
+function _listeners(target, type, unwrap) {
+  var events = target._events;
 
   if (!events)
-    ret = [];
-  else {
-    evlistener = events[type];
-    if (!evlistener)
-      ret = [];
-    else if (typeof evlistener === 'function')
-      ret = [evlistener.listener || evlistener];
-    else
-      ret = unwrapListeners(evlistener);
-  }
+    return [];
 
-  return ret;
+  var evlistener = events[type];
+  if (!evlistener)
+    return [];
+
+  if (typeof evlistener === 'function')
+    return unwrap ? [evlistener.listener || evlistener] : [evlistener];
+
+  return unwrap ? unwrapListeners(evlistener) : arrayClone(evlistener, evlistener.length);
+}
+
+EventEmitter.prototype.listeners = function listeners(type) {
+  return _listeners(this, type, true);
+};
+
+EventEmitter.prototype.rawListeners = function rawListeners(type) {
+  return _listeners(this, type, false);
 };
 
 EventEmitter.listenerCount = function(emitter, type) {

tests/listeners.js

@@ -127,3 +127,23 @@ util.inherits(TestStream, events.EventEmitter);
   assert.ok(Array.isArray(listeners));
   assert.strictEqual(listeners.length, 0);
 }
+
+
+{
+  var ee = new events.EventEmitter();
+  ee.on('foo', listener);
+  var wrappedListener = ee.rawListeners('foo');
+  assert.strictEqual(wrappedListener.length, 1);
+  assert.strictEqual(wrappedListener[0], listener);
+  assert.notStrictEqual(wrappedListener, ee.rawListeners('foo'));
+  ee.once('foo', listener);
+  var wrappedListeners = ee.rawListeners('foo');
+  assert.strictEqual(wrappedListeners.length, 2);
+  assert.strictEqual(wrappedListeners[0], listener);
+  assert.notStrictEqual(wrappedListeners[1], listener);
+  assert.strictEqual(wrappedListeners[1].listener, listener);
+  assert.notStrictEqual(wrappedListeners, ee.rawListeners('foo'));
+  ee.emit('foo');
+  assert.strictEqual(wrappedListeners.length, 2);
+  assert.strictEqual(wrappedListeners[1].listener, listener);
+}