add count method

add count method tests

chain.js

@@ -83,6 +83,14 @@ function Chain(items) {
         return _items;
     }
 
+    function _count(){
+        var length = 0;
+        for(var i in _items){
+            length++;
+        }
+        return length;
+    }
+
     function _goTo(index) {
         index = parseInt(index);
         _index = index < 0 ? _items.length - 1 : index;
@@ -94,6 +102,16 @@ function Chain(items) {
         return _current();
     }
 
+    function _slice(start, length){
+        var out = [];
+        for(var i in _items){
+            if(i >= start && i <= length){
+                out.push(_items[i]);
+            }
+        }
+        return new Chain(out);
+    }
+
     return {
         next        : _next,
         prev        : _prev,
@@ -107,6 +125,8 @@ function Chain(items) {
         goToEnd     : _goToEnd,
         getItems    : _getItems,
         beginFrom   : _beginFrom,
-        getIndex    : _getIndex
+        getIndex    : _getIndex,
+        slice       : _slice,
+        count       : _count
     };
 }

test/test.js

@@ -8,18 +8,40 @@ describe("Testing Chain", function () {
 
         it("expecting shift to -2", function () {
             expect(chain.current()).toBe(-2);
-            expect(chain.current().getIndex()).toBe(3);
+        });
+
+        it("expecting index would be 0", function () {
+            expect(chain.getIndex()).toBe(0);
         });
 
         it("expecting than array length would be 2", function(){
-            expect(chain.getItems().length).toBe(2);
+            expect(chain.getItems().length).toBe(4);
         });
 
         it("expecting than last item would be null", function(){
             expect(chain.last()).toBe(null);
         })
     });
 
+    describe("Begin sub chain", function(){
+        var chain = new Chain(arr);
+
+        var sub_chain = chain.slice(2,4);
+
+        it("subchain must have 4 items ", function(){
+            expect(sub_chain.count()).toBe(3);
+        });
+
+        it("first item will be 1", function(){
+            expect(sub_chain.current()).toBe(3);
+            expect(sub_chain.first()).toBe(3);
+        });
+
+        it("subchain must have last items equal as -2", function(){
+            expect(sub_chain.last()).toBeNull();
+        });
+    });
+
     describe("Items equality", function () {
 
         var chain = new Chain(arr);