@@ -1,31 +1,27 @@
-/* Collatz conjecture */
+"use strict";
 
-function collatz(n) {
-var numbers = []
+/**known Collatz infinite loops*/
+const CYCLES = new Set([
+1, 0, -1, -5, -17, NaN, Infinity, -Infinity
+]);
 
-while (n > 1) {
-numbers.push(n)
-if (n % 2 === 0) {
-n = n / 2;
-} else {
-n = (3 * n) + 1;
-}
+/**
+* Collatz conjecture calculator.
+* returns an array containing the Hailstone sequence of `n`.
+* @param {number} n "seed"
+*/
+const collatz = n => {
+const sequence = [];
+
+while ( !CYCLES.has(n) ) {
+sequence.push(n);
+n = n % 2 === 0 ? n / 2 : 3 * n + 1;
 }
-numbers.push(n)
-return numbers
+sequence.push(n);
+return sequence;
 }
 
-console.log(
-'Collatz conjecture for n = 11',
-collatz(11)
-)
-
-console.log(
-'Collatz conjecture for n = 27',
-collatz(27)
-)
-
-console.log(
-'Collatz conjecture for n = 51',
-collatz(51)
-)
+[11, 27, 51, -7].forEach(n => console.log(
+`Hailstone sequence of ${n}`,
+collatz(n)
+));