allow replacing null keys with specified value in groupBy filter

src/_filter/collection/group-by.js

@@ -5,16 +5,23 @@
  *
  * @description
  * Create an object composed of keys generated from the result of running each element of a collection,
- * each key is an array of the elements.
+ * each key is an array of the elements.  Specify null replacement to control sort behavior for null/undefined keys.
  */
 
 angular.module('a8m.group-by', [ 'a8m.filter-watcher' ])
 
   .filter('groupBy', [ '$parse', 'filterWatcher', function ( $parse, filterWatcher ) {
-    return function (collection, property) {
+    return function (collection, property, nullReplacement) {
 
       var result,
-        get = $parse(property),
+        getParse = $parse(property),
+        get = function(el) {
+          var val = getParse(el);
+          if(nullReplacement !== undefined && (val == null || val == undefined)){
+            return nullReplacement;
+          }
+          return val;
+        },
         prop;
 
       if(!isObject(collection) || isUndefined(property)) {

test/spec/filter/collection/group-by.js

@@ -73,4 +73,66 @@ describe('groupByFilter', function() {
 
   });
 
+  it('should replace null when asked, get array as collection, property(nested to) as identifier and ' +
+    'returns the composed aggregate object.', function() {
+
+    var players = [
+      {name: 'Gene', team: 'alpha'},
+      {name: 'George', team: 'beta'},
+      {name: 'Steve', team: 'gamma'},
+      {name: 'Paula', team: 'beta'},
+      {name: 'Scruath', team: 'gamma'},
+      {name: 'Alex', team: null },
+      {name: 'Rob' },
+      {name: 'Sven', team: false }
+    ];
+
+    expect(filter(players, 'team', 'a')).toEqual( {
+      a: [players[5], players[6]],
+      alpha: [players[0]],
+      beta: [players[1], players[3]],
+      gamma: [players[2], players[4]],
+      'false': [players[7]]
+    });
+
+  });
+
+  it('should replace null when asked, support nested properties to', function() {
+    var orders = [
+      { id:10, customer: { name: 'foo', id: 1 } },
+      { id:11, customer: { name: 'bar', id: 2 } },
+      { id:12, customer: { name: 'foo', id: 1 } },
+      { id:13, customer: { name: 'bar', id: 2 } },
+      { id:14, customer: { name: 'bar', id: 3 } },
+      { id:15, customer: { name: null } },
+      { id:16, customer: {} },
+      2, null, true
+    ];
+
+    expect(filter(orders, 'customer.name', 0)).toEqual( {
+      foo: [orders[0], orders[2]],
+      bar: [orders[1], orders[3], orders[4]],
+      0: [orders[5], orders[6], 2, null, true]
+    });
+
+  });
+
+
+  it('should replace null when asked, get object as collection, property(nested to) as identifier and ' +
+    'returns the composed aggregate object.', function() {
+    var dataObject = {
+      0: { id: 1, data: {} },
+      1: { id: 1, data: {} },
+      2: { id: 2, data: {} },
+      3: { id: 2, data: {} },
+      4: { id: null, data: {} }
+    };
+
+    expect(filter(dataObject, 'id', 0)).toEqual({
+      0: [dataObject[4]],
+      1: [dataObject[0], dataObject[1]],
+      2: [dataObject[2], dataObject[3]]
+    });
+
+  });
 });