add isPrime

snippets/isPrime.md

@@ -0,0 +1,14 @@
+### isPrime
+
+Checks if the provided intiger is primer number.
+
+Returns `false` if the provided number has positive divisors other than 1 and itself or if the number itself is less than 2.
+
+```js
+const isPrime = num =>
+  for (var i = 2; i < num; i++) if (num % i == 0) return false;
+  return num >= 2;
+// isPrime(11) -> true
+// isPrime(12) -> false
+// isPrime(1) -> false
+```