Bump to v4.0.0.

transform.js

@@ -0,0 +1,60 @@
+import arrayEach from './internal/arrayEach';
+import baseCreate from './internal/baseCreate';
+import baseForOwn from './internal/baseForOwn';
+import baseIteratee from './internal/baseIteratee';
+import isArray from './isArray';
+import isFunction from './isFunction';
+import isObject from './isObject';
+import isTypedArray from './isTypedArray';
+
+/**
+ * An alternative to `_.reduce`; this method transforms `object` to a new
+ * `accumulator` object which is the result of running each of its own enumerable
+ * properties through `iteratee`, with each invocation potentially mutating
+ * the `accumulator` object. The iteratee is invoked with four arguments:
+ * (accumulator, value, key, object). Iteratee functions may exit iteration
+ * early by explicitly returning `false`.
+ *
+ * @static
+ * @memberOf _
+ * @category Object
+ * @param {Array|Object} object The object to iterate over.
+ * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+ * @param {*} [accumulator] The custom accumulator value.
+ * @returns {*} Returns the accumulated value.
+ * @example
+ *
+ * _.transform([2, 3, 4], function(result, n) {
+ *   result.push(n *= n);
+ *   return n % 2 == 0;
+ * });
+ * // => [4, 9]
+ *
+ * _.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
+ *   (result[value] || (result[value] = [])).push(key);
+ * });
+ * // => { '1': ['a', 'c'], '2': ['b'] }
+ */
+function transform(object, iteratee, accumulator) {
+  var isArr = isArray(object) || isTypedArray(object);
+  iteratee = baseIteratee(iteratee, 4);
+
+  if (accumulator == null) {
+    if (isArr || isObject(object)) {
+      var Ctor = object.constructor;
+      if (isArr) {
+        accumulator = isArray(object) ? new Ctor : [];
+      } else {
+        accumulator = baseCreate(isFunction(Ctor) ? Ctor.prototype : undefined);
+      }
+    } else {
+      accumulator = {};
+    }
+  }
+  (isArr ? arrayEach : baseForOwn)(object, function(value, index, object) {
+    return iteratee(accumulator, value, index, object);
+  });
+  return accumulator;
+}
+
+export default transform;