ran npm run tdd & generated TDD

test/isSorted/isSorted.js

@@ -0,0 +1,6 @@
+module.exports = arr => {
+const direction = arr[0] > arr[1] ? -1 : 1;
+for (let [i, val] of arr.entries())
+if (i === arr.length - 1) return direction;
+else if ((val - arr[i + 1]) * direction > 0) return 0;
+};