allow removing of components in merge via undefined or null

index.js

@@ -31,7 +31,7 @@ docuri.parts = function(obj) {
     return obj[part];
   });
 
-  while (parts.length && typeof parts[parts.length - 1] === 'undefined') {
+  while (parts.length && (typeof parts[parts.length - 1] === 'undefined' || parts[parts.length - 1] === null)) {
     parts.pop();
   }
 
@@ -64,7 +64,7 @@ docuri.merge = function(obj, objToMerge) {
   }
 
   DEFINITION.forEach(function(part) {
-    if (objToMerge[part]) {
+    if (part in objToMerge) {
       obj[part] = objToMerge[part];
     }
   });

package.json

@@ -1,6 +1,6 @@
 {
   "name": "docuri",
-  "version": "3.0.1",
+  "version": "3.0.2",
   "description": "Rich document ids for CouchDB",
   "main": "index.js",
   "scripts": {

test/merge_test.js

@@ -49,3 +49,14 @@ test('changing type component using object', function(t) {
   t.end();
 });
 
+test('removing component with undefined', function(t) {
+  t.equal(merge('type/id/subtype/index/version', {version:undefined}), 'type/id/subtype/index', 'should return docuri string with version removed');
+  t.end();
+});
+
+test('removing component with null', function(t) {
+  t.equal(merge('type/id/subtype/index/version', {version:null}), 'type/id/subtype/index', 'should return docuri string with version removed');
+  t.end();
+});
+
+