emitting an event when status of timer changes (#2)

* Update index.js

* Update README.md

emitting an event when status of timer changes

* Update index.js

updated as per suggestions

* Update README.md

updated as per suggestion

README.md

@@ -22,7 +22,7 @@ let timer = new Timer()
 
 timer.on('tick', (ms) => console.log('tick', ms))
 timer.on('done', () => console.log('done!'))
-
+timer.on('statusChanged', (status) => console.log('status:', status))
 timer.start(5000) // run for 5 seconds
 ```
 
@@ -52,6 +52,9 @@ Event emitted every `interval` with the current time in ms.
 ### `timer.on('done', () => {})`
 Event emitted when the timer reaches the `duration` set by calling `timer.start()`.
 
+### `timer.on('statusChanged', (status) => {})`
+Event emitted when the timer status changes.
+
 ## properties
 
 ### `timer.time`

src/index.js

@@ -28,27 +28,32 @@ class Timer extends EventEmitter {
     if (duration == null) throw new TypeError('must provide duration parameter')
     this._duration = duration
     this._endTime = Date.now() + duration
-    this._status = 'running'
+    this._changeStatus('running')
     this.emit('tick', this._stopwatch ? 0 : this._duration)
     this._timeoutID = setInterval(tick.bind(this), interval || this._interval)
   }
 
   stop () {
     clearInterval(this._timeoutID)
-    this._status = 'stopped'
+    this._changeStatus('stopped')
   }
 
   pause () {
     if (this._status !== 'running') return
     this._pauseTime = Date.now()
-    this._status = 'paused'
+    this._changeStatus('paused')
   }
 
   resume () {
     if (this._status !== 'paused') return
     this._endTime += Date.now() - this._pauseTime
     this._pauseTime = 0
-    this._status = 'running'
+    this._changeStatus('running')
+  }
+
+  _changeStatus (status) {
+    this._status = status
+    this.emit('statusChanged', this._status)
   }
 
   get time () {