add hw2

node_modules/ramda/es/countBy.js

@@ -0,0 +1,32 @@
+import reduceBy from "./reduceBy.js";
+/**
+ * Counts the elements of a list according to how many match each value of a
+ * key generated by the supplied function. Returns an object mapping the keys
+ * produced by `fn` to the number of occurrences in the list. Note that all
+ * keys are coerced to strings because of how JavaScript objects work.
+ *
+ * Acts as a transducer if a transformer is given in list position.
+ *
+ * @func
+ * @memberOf R
+ * @since v0.1.0
+ * @category Relation
+ * @sig (a -> String) -> [a] -> {*}
+ * @param {Function} fn The function used to map values to keys.
+ * @param {Array} list The list to count elements from.
+ * @return {Object} An object mapping keys to number of occurrences in the list.
+ * @example
+ *
+ *      const numbers = [1.0, 1.1, 1.2, 2.0, 3.0, 2.2];
+ *      R.countBy(Math.floor)(numbers);    //=> {'1': 3, '2': 2, '3': 1}
+ *
+ *      const letters = ['a', 'b', 'A', 'a', 'B', 'c'];
+ *      R.countBy(R.toLower)(letters);   //=> {'a': 3, 'b': 2, 'c': 1}
+ */
+
+var countBy =
+/*#__PURE__*/
+reduceBy(function (acc, elem) {
+  return acc + 1;
+}, 0);
+export default countBy;