Bump to v3.0.0.

collection/groupBy.js

@@ -0,0 +1,52 @@
+import createAggregator from '../internal/createAggregator';
+
+/** Used for native method references. */
+var objectProto = Object.prototype;
+
+/** Used to check objects for own properties. */
+var hasOwnProperty = objectProto.hasOwnProperty;
+
+/**
+ * Creates an object composed of keys generated from the results of running
+ * each element of `collection` through `iteratee`. The corresponding value
+ * of each key is an array of the elements responsible for generating the key.
+ * The `iteratee` is bound to `thisArg` and invoked with three arguments;
+ * (value, index|key, collection).
+ *
+ * If a property name is provided for `predicate` the created "_.property"
+ * style callback returns the property value of the given element.
+ *
+ * If an object is provided for `predicate` the created "_.matches" style
+ * callback returns `true` for elements that have the properties of the given
+ * object, else `false`.
+ *
+ * @static
+ * @memberOf _
+ * @category Collection
+ * @param {Array|Object|string} collection The collection to iterate over.
+ * @param {Function|Object|string} [iteratee=_.identity] The function invoked
+ *  per iteration. If a property name or object is provided it is used to
+ *  create a "_.property" or "_.matches" style callback respectively.
+ * @param {*} [thisArg] The `this` binding of `iteratee`.
+ * @returns {Object} Returns the composed aggregate object.
+ * @example
+ *
+ * _.groupBy([4.2, 6.1, 6.4], function(n) { return Math.floor(n); });
+ * // => { '4': [4.2], '6': [6.1, 6.4] }
+ *
+ * _.groupBy([4.2, 6.1, 6.4], function(n) { return this.floor(n); }, Math);
+ * // => { '4': [4.2], '6': [6.1, 6.4] }
+ *
+ * // using the "_.property" callback shorthand
+ * _.groupBy(['one', 'two', 'three'], 'length');
+ * // => { '3': ['one', 'two'], '5': ['three'] }
+ */
+var groupBy = createAggregator(function(result, value, key) {
+  if (hasOwnProperty.call(result, key)) {
+    result[key].push(value);
+  } else {
+    result[key] = [value];
+  }
+});
+
+export default groupBy;