more work

node_modules/lodash/internal/createAggregator.js

@@ -0,0 +1,40 @@
+var baseCallback = require('./baseCallback'),
+    baseEach = require('./baseEach'),
+    isArray = require('../lang/isArray');
+
+/**
+ * Creates a function that aggregates a collection, creating an accumulator
+ * object composed from the results of running each element in the collection
+ * through an iteratee.
+ *
+ * **Note:** This function is used to create `_.countBy`, `_.groupBy`, `_.indexBy`,
+ * and `_.partition`.
+ *
+ * @private
+ * @param {Function} setter The function to set keys and values of the accumulator object.
+ * @param {Function} [initializer] The function to initialize the accumulator object.
+ * @returns {Function} Returns the new aggregator function.
+ */
+function createAggregator(setter, initializer) {
+  return function(collection, iteratee, thisArg) {
+    var result = initializer ? initializer() : {};
+    iteratee = baseCallback(iteratee, thisArg, 3);
+
+    if (isArray(collection)) {
+      var index = -1,
+          length = collection.length;
+
+      while (++index < length) {
+        var value = collection[index];
+        setter(result, value, iteratee(value, index, collection), collection);
+      }
+    } else {
+      baseEach(collection, function(value, key, collection) {
+        setter(result, value, iteratee(value, key, collection), collection);
+      });
+    }
+    return result;
+  };
+}
+
+module.exports = createAggregator;