Allow user to specify the step interval

lib/countdown.js

@@ -3,22 +3,31 @@
 
   var root = this;
 
-  var Countdown = function(duration, onTick, onComplete) {
+  var Countdown = function(duration, onTick, onComplete, step) {
     var secondsLeft = Math.round(duration)
+        , step = (step > 0) ? Math.round(step) : 1
         , tick = function() {
           if (secondsLeft > 0) {
-              onTick(secondsLeft);
-              secondsLeft -= 1;
+            onTick(secondsLeft);
+            if (secondsLeft >= step) {
+              secondsLeft -= step;
+            }
+            else {
+              // Clear the current interval, and start it up with the the remaining seconds left.
+              clearInterval(interval);
+              interval = setInterval(
+                function() { tick.call(this) }, 1000 * secondsLeft, this
+              );
+              secondsLeft = 0;
+            }
           } else {
               clearInterval(interval);
               onComplete();
           }
         }
         // Setting the interval, by call tick and passing through this via a self-calling function wrap.
         , interval = setInterval(
-          (function(self){
-            return function() { tick.call(self); };
-          })(this), 1000
+          function() { tick.call(this) }, 1000 * step, this
         );
 
     // First tick.

test/test.js

@@ -33,6 +33,49 @@ describe("countdown.js", function() {
       assert(tickFunction.callCount == 5);
     });
 
+    it("executes onTick while countdown is running with user specified step interval", function() {
+      new Countdown(5, tickFunction, callbackFunction, 2);
+      assert(tickFunction.callCount == 1);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 1);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 2);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 2);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 3);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 3);
+    });
+
+    it("defaults to 1 second ticks with invalid step parameter", function() {
+      new Countdown(2, tickFunction, callbackFunction, -1);
+      assert(tickFunction.callCount == 1);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 2);
+      clock.tick(1000);
+      new Countdown(2, tickFunction, callbackFunction, []);
+      assert(tickFunction.callCount == 3);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 4);
+      clock.tick(1000);
+      new Countdown(2, tickFunction, callbackFunction, {});
+      assert(tickFunction.callCount == 5);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 6);
+      clock.tick(1000);
+      new Countdown(2, tickFunction, callbackFunction, 'invalid');
+      assert(tickFunction.callCount == 7);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 8);
+      clock.tick(1000);
+      new Countdown(2, tickFunction, callbackFunction, true);
+      assert(tickFunction.callCount == 9);
+      clock.tick(1000);
+      assert(tickFunction.callCount == 10);
+      clock.tick(1000);
+    });
+
     it("executes onComplete", function() {
       new Countdown(5, tickFunction, callbackFunction);
       clock.tick(4000);