Refactor

lib/util.ts

@@ -0,0 +1,16 @@
+/** pick up to random N elements from array.
+ *  just shuffle it if N is unspecified or greater than the length of the array.
+ *  the original array remains unmodified. */
+export function sample<T>(arr: T[], n: number = arr.length): T[] {
+  if (n > arr.length) return sample(arr, arr.length);
+  const copy = [...arr];
+  for (let i = 0; i < n; i++) {
+    const j = i + Math.floor(Math.random() * (copy.length - i));
+    [copy[i], copy[j]] = [copy[j] as T, copy[i] as T];
+  }
+  return copy.slice(0, n);
+}
+
+/** sleep for N milliseconds */
+export const sleep = (msec: number) =>
+  new Promise((resolve) => setTimeout(resolve, msec));