3 files changed, 5 insertions, 4 deletions
diff --git a/packages/backend/src/misc/prelude/array.ts b/packages/backend/src/misc/prelude/array.ts
index 0b2830cb7b..2524eacfb3 100644
--- a/packages/backend/src/misc/prelude/array.ts
+++ b/packages/backend/src/misc/prelude/array.ts
@@ -67,8 +67,9 @@ export function maximum(xs: number[]): number {
 export function groupBy<T>(f: EndoRelation<T>, xs: T[]): T[][] {
 	const groups = [] as T[][];
 	for (const x of xs) {
-		if (groups.length !== 0 && f(groups[groups.length - 1][0], x)) {
-			groups[groups.length - 1].push(x);
+		const lastGroup = groups.at(-1);
+		if (lastGroup !== undefined && f(lastGroup[0], x)) {
+			lastGroup.push(x);
 		} else {
 			groups.push([x]);
 		}
diff --git a/packages/backend/src/misc/prelude/await-all.ts b/packages/backend/src/misc/prelude/await-all.ts
index b955c3a5d8..fd9832d6f8 100644
--- a/packages/backend/src/misc/prelude/await-all.ts
+++ b/packages/backend/src/misc/prelude/await-all.ts
@@ -10,7 +10,7 @@ export async function awaitAll<T>(obj: Promiseable<T>): Promise<T> {
 	const resolvedValues = await Promise.all(values.map(value =>
 		(!value || !value.constructor || value.constructor.name !== 'Object')
 			? value
-			: awaitAll(value)
+			: awaitAll(value),
 	));
 
 	for (let i = 0; i < keys.length; i++) {
diff --git a/packages/backend/src/misc/prelude/url.ts b/packages/backend/src/misc/prelude/url.ts
index 9b1dabc789..5239678280 100644
--- a/packages/backend/src/misc/prelude/url.ts
+++ b/packages/backend/src/misc/prelude/url.ts
@@ -2,7 +2,7 @@
  * 1. 配列に何も入っていない時はクエリを付けない
  * 2. プロパティがundefinedの時はクエリを付けない
  * （new URLSearchParams(obj)ではそこまで丁寧なことをしてくれない）
- */ 
+ */
 export function query(obj: Record<string, unknown>): string {
 	const params = Object.entries(obj)
 		.filter(([, v]) => Array.isArray(v) ? v.length : v !== undefined)