Merge pull request #14 from butterflyhug/fix-startof

Fix frozenMoment methods where moment uses mutators internally

Author: butterflyhug

frozen-moment.js

@@ -83,13 +83,17 @@
 
   function frozenMethodGenerator(name) {
     return function () {
-      return momentProto[name].apply(this.freeze(), arguments);
+      var thawed = this.thaw();
+      var result = thawed[name].apply(thawed, arguments);
+      return (moment.isMoment(result) ? result.freeze() : result);
     };
   }
   function frozenIfArgumentsMethodGenerator(name) {
     return function () {
       if (arguments.length) {
-        return momentProto[name].apply(this.freeze(), arguments);
+        var thawed = this.thaw();
+        var result = thawed[name].apply(thawed, arguments);
+        return (moment.isMoment(result) ? result.freeze() : result);
       }
       return momentProto[name].apply(this);
     };

test.js

@@ -57,6 +57,11 @@ assert(frozenClone.thaw, 'cloning frozen moment creates another frozen moment');
 frozenClone.add(1, 'days');
 assert(frozenClone.isSame(frozen), 'mutators do not change value of cloned frozen moment');
 
+var frozenStartOfYear = moment.frozen('2015-11-09T09:44:04').startOf('year');
+assert(frozenStartOfYear.valueOf() === moment('2015-01-01T00:00:00').valueOf(), 'start of year is calculated accurately');
+
+assert(frozenStartOfYear.format().substr(0, 19) === '2015-01-01T00:00:00', 'format works with frozen moment')
+
 
 // prototype chain and moment.frozen.fn