Categorize patterns

utils/randomIterms.ts

@@ -0,0 +1,14 @@
+type Tuple<T> = [number, T[]];
+
+export function randomItems<T>(arr: T[], count: number): T[] {
+    const result = arr.concat().reduce(
+        (p, _, __, arr) => {
+            const [a, b] = p;
+            return (a < count)
+                    ? [a + 1, b.concat(arr.splice(Math.random() * arr.length | 0, 1))]
+                    : p;
+        },
+        [0, []] as Tuple<T>
+    );
+    return (result as Tuple<T>)[1];
+};