Add arethusaUtil.inject

app/js/arethusa_util.js

@@ -21,6 +21,15 @@ var arethusaUtil = {
     return result;
   },
 
+  // inject like ruby - or more like each_with_object
+  // Take care - will not work with immutable memos!
+  inject: function(memo, container, fn){
+    container.forEach(function(el) {
+      fn(memo, el);
+    });
+    return memo;
+  },
+
   // flat push
   pushAll: function(target, pusher) {
     target.push.apply(target, pusher);

spec/arethusa_util_spec.js

@@ -35,6 +35,26 @@ describe("arethusaUtil", function() {
     });
   });
 
+  describe('inject', function() {
+    it('works like a ruby each_with_object', function() {
+      var coll = [1, 2, 3];
+      var fn = function(memo, el) {
+        memo.push(el + 1);
+      };
+      var res = [2, 3, 4];
+      expect(arethusaUtil.inject([], coll, fn)).toEqual(res);
+    });
+
+    it("will not work with immutable objects", function() {
+      var coll = [1, 2, 3];
+      var fn = function(memo, el) {
+        memo += el;
+      };
+      expect(arethusaUtil.inject(0, coll, fn)).toEqual(0);
+      expect(arethusaUtil.inject(0, coll, fn)).not.toEqual(6);
+    });
+  });
+
   describe('pushAll', function() {
     it('flat-pushes all elements of an array into another', function() {
       var arr1 = [1, 2];