diff --git a/src/EventEmitter.js b/src/EventEmitter.js
deleted file mode 100644
index 3661894..0000000
--- a/src/EventEmitter.js
+++ /dev/null
@@ -1,64 +0,0 @@
-/**
- * @license MIT
- */
-
-function EventEmitter() {
-  this._events = this._events || {};
-}
-
-EventEmitter.prototype.addListener = function(type, listener) {
-  this._events[type] = this._events[type] || [];
-  this._events[type].push(listener);
-};
-
-EventEmitter.prototype.on = EventEmitter.prototype.addListener;
-
-EventEmitter.prototype.removeListener = function(type, listener) {
-  if (!this._events[type]) return;
-
-  var obj = this._events[type]
-  , i = obj.length;
-
-  while (i--) {
-    if (obj[i] === listener || obj[i].listener === listener) {
-      obj.splice(i, 1);
-      return;
-    }
-  }
-};
-
-EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
-
-EventEmitter.prototype.removeAllListeners = function(type) {
-  if (this._events[type]) delete this._events[type];
-};
-
-EventEmitter.prototype.once = function(type, listener) {
-  var self = this;
-  function on() {
-    var args = Array.prototype.slice.call(arguments);
-    this.removeListener(type, on);
-    return listener.apply(this, args);
-  }
-  on.listener = listener;
-  return this.on(type, on);
-};
-
-EventEmitter.prototype.emit = function(type) {
-  if (!this._events[type]) return;
-
-  var args = Array.prototype.slice.call(arguments, 1)
-  , obj = this._events[type]
-  , l = obj.length
-  , i = 0;
-
-  for (; i < l; i++) {
-    obj[i].apply(this, args);
-  }
-};
-
-EventEmitter.prototype.listeners = function(type) {
-  return this._events[type] = this._events[type] || [];
-};
-
-export { EventEmitter };
diff --git a/src/EventEmitter.test.ts b/src/EventEmitter.test.ts
new file mode 100644
index 0000000..7ae381c
--- /dev/null
+++ b/src/EventEmitter.test.ts
@@ -0,0 +1,84 @@
+import { assert } from 'chai';
+import { EventEmitter } from './EventEmitter';
+
+describe('EventEmitter', () => {
+  let eventEmitter: EventEmitter;
+
+  beforeEach(() => {
+    eventEmitter = new EventEmitter();
+  });
+
+  describe('once', () => {
+    it('should trigger the listener only once', () => {
+      let count = 0;
+      const listener = () => count++;
+      eventEmitter.once('test', listener);
+      eventEmitter.emit('test');
+      assert.equal(count, 1);
+      eventEmitter.emit('test');
+      assert.equal(count, 1);
+    });
+  });
+
+  describe('emit', () => {
+    it('should emit events to listeners', () => {
+      let count1 = 0;
+      let count2 = 0;
+      const listener1 = () => count1++;
+      const listener2 = () => count2++;
+      eventEmitter.on('test', listener1);
+      eventEmitter.on('test', listener2);
+      eventEmitter.emit('test');
+      assert.equal(count1, 1);
+      assert.equal(count2, 1);
+      eventEmitter.emit('test');
+      assert.equal(count1, 2);
+      assert.equal(count2, 2);
+    });
+
+    it('should manage multiple listener types', () => {
+      let count1 = 0;
+      let count2 = 0;
+      const listener1 = () => count1++;
+      const listener2 = () => count2++;
+      eventEmitter.on('test', listener1);
+      eventEmitter.on('foo', listener2);
+      eventEmitter.emit('test');
+      assert.equal(count1, 1);
+      assert.equal(count2, 0);
+      eventEmitter.emit('foo');
+      assert.equal(count1, 1);
+      assert.equal(count2, 1);
+    });
+  });
+
+  describe('listeners', () => {
+    it('should return listeners for the type requested', () => {
+      assert.equal(eventEmitter.listeners('test').length, 0);
+      const listener = () => {};
+      eventEmitter.on('test', listener);
+      assert.deepEqual(eventEmitter.listeners('test'), [listener]);
+    });
+  });
+
+  describe('off', () => {
+    it('should remove the specific listener', () => {
+      const listener1 = () => {};
+      const listener2 = () => {};
+      eventEmitter.on('foo', listener1);
+      eventEmitter.on('foo', listener2);
+      assert.equal(eventEmitter.listeners('foo').length, 2);
+      eventEmitter.off('foo', listener1);
+      assert.deepEqual(eventEmitter.listeners('foo'), [listener2]);
+    });
+  });
+
+  describe('removeAllListeners', () => {
+    it('should clear all listeners', () => {
+      eventEmitter.on('foo', () => {});
+      assert.equal(eventEmitter.listeners('foo').length, 1);
+      eventEmitter.removeAllListeners('foo');
+      assert.equal(eventEmitter.listeners('foo').length, 0);
+    });
+  });
+});
diff --git a/src/EventEmitter.ts b/src/EventEmitter.ts
new file mode 100644
index 0000000..d05e386
--- /dev/null
+++ b/src/EventEmitter.ts
@@ -0,0 +1,70 @@
+/**
+ * @license MIT
+ */
+
+interface ListenerType {
+    (): void;
+    listener?: () => void;
+};
+
+export class EventEmitter {
+  private _events: {[type: string]: ListenerType[]};
+
+  constructor() {
+    this._events = {};
+  }
+
+  public on(type, listener): void {
+    this._events[type] = this._events[type] || [];
+    this._events[type].push(listener);
+  }
+
+  public off(type, listener): void {
+    if (!this._events[type]) {
+      return;
+    }
+
+    let obj = this._events[type];
+    let i = obj.length;
+
+    while (i--) {
+      if (obj[i] === listener || obj[i].listener === listener) {
+        obj.splice(i, 1);
+        return;
+      }
+    }
+  }
+
+  public removeAllListeners(type): void {
+    if (this._events[type]) {
+       delete this._events[type];
+    }
+  }
+
+  public once(type, listener): any {
+    function on() {
+      let args = Array.prototype.slice.call(arguments);
+      this.off(type, on);
+      return listener.apply(this, args);
+    }
+    (<any>on).listener = listener;
+    return this.on(type, on);
+  }
+
+  public emit(type): void {
+    if (!this._events[type]) {
+      return;
+    }
+
+    let args = Array.prototype.slice.call(arguments, 1);
+    let obj = this._events[type];
+
+    for (let i = 0; i < obj.length; i++) {
+      obj[i].apply(this, args);
+    }
+  }
+
+  public listeners(type): ListenerType[] {
+    return this._events[type] || [];
+  }
+}