Test migration to jest by hand

Apparently using regular expressions is way easier.

test/mapObject/mapObject.js

@@ -0,0 +1,5 @@
+const mapObject = (arr, fn) =>
+(a => (
+(a = [arr, arr.map(fn)]), a[0].reduce((acc, val, ind) => ((acc[val] = a[1][ind]), acc), {})
+))();
+module.exports = mapObject;