From 6efea94dd04393c7b21bfb97b700c1bc0ee47a00 Mon Sep 17 00:00:00 2001
From: Pascal Syma <pascal@syma.dev>
Date: Thu, 5 Dec 2024 11:15:51 +0100
Subject: [PATCH] Add getMiddleElement array util

---
 utils/array.test.ts | 14 +++++++++++++-
 utils/array.ts      | 17 +++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/utils/array.test.ts b/utils/array.test.ts
index 46ceee8..b25e365 100644
--- a/utils/array.test.ts
+++ b/utils/array.test.ts
@@ -1,5 +1,11 @@
 import { describe, expect, it } from 'bun:test';
-import { multArray, multBy, sumArray, sumBy } from './array.ts';
+import {
+  getMiddleElement,
+  multArray,
+  multBy,
+  sumArray,
+  sumBy
+} from './array.ts';
 
 describe('array utils', () => {
   it('sumArray number array', () => {
@@ -127,4 +133,10 @@ describe('array utils', () => {
     expect(multBy([], (e) => e)).toBeFinite();
     expect(multBy([], (e) => e)).toBe(0);
   });
+  it('getMiddleElement', () => {
+    expect(getMiddleElement([1, 2, 3, 4])).toBe(3);
+    expect(getMiddleElement([1, 2, 3])).toBe(2);
+    expect(getMiddleElement([1])).toBe(1);
+    expect(getMiddleElement([])).toBeUndefined();
+  });
 });
diff --git a/utils/array.ts b/utils/array.ts
index 09f6b7d..f56c7ed 100644
--- a/utils/array.ts
+++ b/utils/array.ts
@@ -73,3 +73,20 @@ export function groupBy<E, K>(
     [] as { key: K; elements: Array<E> }[]
   );
 }
+
+/**
+ * Return the middle Element of an array, rounding up.
+ * Returns undefined for empty arrays without throwing!
+ *
+ * @example
+ * ```typescript
+ * getMiddleElement([1, 2, 3, 4]) === 3
+ * getMiddleElement([1, 2, 3]) === 2
+ * getMiddleElement([1]) === 1
+ * getMiddleElement([]) === undefined
+ * ```
+ * @param arr
+ */
+export function getMiddleElement<E>(arr: ReadonlyArray<E>) {
+  return arr[Math.floor(arr.length / 2)];
+}