add hw2

node_modules/lodash-es/invertBy.js

@@ -0,0 +1,56 @@
+import baseIteratee from './_baseIteratee.js';
+import createInverter from './_createInverter.js';
+
+/** Used for built-in method references. */
+var objectProto = Object.prototype;
+
+/** Used to check objects for own properties. */
+var hasOwnProperty = objectProto.hasOwnProperty;
+
+/**
+ * Used to resolve the
+ * [`toStringTag`](http://ecma-international.org/ecma-262/7.0/#sec-object.prototype.tostring)
+ * of values.
+ */
+var nativeObjectToString = objectProto.toString;
+
+/**
+ * This method is like `_.invert` except that the inverted object is generated
+ * from the results of running each element of `object` thru `iteratee`. The
+ * corresponding inverted value of each inverted key is an array of keys
+ * responsible for generating the inverted value. The iteratee is invoked
+ * with one argument: (value).
+ *
+ * @static
+ * @memberOf _
+ * @since 4.1.0
+ * @category Object
+ * @param {Object} object The object to invert.
+ * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+ * @returns {Object} Returns the new inverted object.
+ * @example
+ *
+ * var object = { 'a': 1, 'b': 2, 'c': 1 };
+ *
+ * _.invertBy(object);
+ * // => { '1': ['a', 'c'], '2': ['b'] }
+ *
+ * _.invertBy(object, function(value) {
+ *   return 'group' + value;
+ * });
+ * // => { 'group1': ['a', 'c'], 'group2': ['b'] }
+ */
+var invertBy = createInverter(function(result, value, key) {
+  if (value != null &&
+      typeof value.toString != 'function') {
+    value = nativeObjectToString.call(value);
+  }
+
+  if (hasOwnProperty.call(result, value)) {
+    result[value].push(key);
+  } else {
+    result[value] = [key];
+  }
+}, baseIteratee);
+
+export default invertBy;