Bump to v4.0.0.

reduce.js

@@ -0,0 +1,49 @@
+import arrayReduce from './internal/arrayReduce';
+import baseEach from './internal/baseEach';
+import baseIteratee from './internal/baseIteratee';
+import baseReduce from './internal/baseReduce';
+import isArray from './isArray';
+
+/**
+ * Reduces `collection` to a value which is the accumulated result of running
+ * each element in `collection` through `iteratee`, where each successive
+ * invocation is supplied the return value of the previous. If `accumulator`
+ * is not provided the first element of `collection` is used as the initial
+ * value. The iteratee is invoked with four arguments:
+ * (accumulator, value, index|key, collection).
+ *
+ * Many lodash methods are guarded to work as iteratees for methods like
+ * `_.reduce`, `_.reduceRight`, and `_.transform`.
+ *
+ * The guarded methods are:
+ * `assign`, `defaults`, `defaultsDeep`, `includes`, `merge`, `orderBy`,
+ * and `sortBy`
+ *
+ * @static
+ * @memberOf _
+ * @category Collection
+ * @param {Array|Object} collection The collection to iterate over.
+ * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+ * @param {*} [accumulator] The initial value.
+ * @returns {*} Returns the accumulated value.
+ * @example
+ *
+ * _.reduce([1, 2], function(sum, n) {
+ *   return sum + n;
+ * });
+ * // => 3
+ *
+ * _.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
+ *   (result[value] || (result[value] = [])).push(key);
+ *   return result;
+ * }, {});
+ * // => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)
+ */
+function reduce(collection, iteratee, accumulator) {
+  var func = isArray(collection) ? arrayReduce : baseReduce,
+      initFromCollection = arguments.length < 3;
+
+  return func(collection, baseIteratee(iteratee, 4), accumulator, initFromCollection, baseEach);
+}
+
+export default reduce;