Test migration to jest by hand

Apparently using regular expressions is way easier.

test/primes/primes.js

@@ -0,0 +1,8 @@
+const primes = num => {
+let arr = Array.from({ length: num - 1 }).map((x, i) => i + 2),
+sqroot = Math.floor(Math.sqrt(num)),
+numsTillSqroot = Array.from({ length: sqroot - 1 }).map((x, i) => i + 2);
+numsTillSqroot.forEach(x => (arr = arr.filter(y => y % x !== 0 || y === x)));
+return arr;
+};
+module.exports = primes;