refactor: 可読性のため一部で`Array.prototype.at`を使うように (#11274)

* refactor: `Array.prototype.at`を使うように

* fixup! refactor: `Array.prototype.at`を使うように

7 files changed, 18 insertions, 17 deletions

diff --git a/packages/frontend/src/components/MkDrive.vue b/packages/frontend/src/components/MkDrive.vue
index 201a6ccdc8..aff227da40 100644
--- a/packages/frontend/src/components/MkDrive.vue
+++ b/packages/frontend/src/components/MkDrive.vue
@@ -568,7 +568,7 @@ function fetchMoreFolders() {
 	os.api('drive/folders', {
 		folderId: folder.value ? folder.value.id : null,
 		type: props.type,
-		untilId: folders.value[folders.value.length - 1].id,
+		untilId: folders.value.at(-1)?.id,
 		limit: max + 1,
 	}).then(folders => {
 		if (folders.length === max + 1) {
@@ -591,7 +591,7 @@ function fetchMoreFiles() {
 	os.api('drive/files', {
 		folderId: folder.value ? folder.value.id : null,
 		type: props.type,
-		untilId: files.value[files.value.length - 1].id,
+		untilId: files.value.at(-1)?.id,
 		limit: max + 1,
 	}).then(files => {
 		if (files.length === max + 1) {
diff --git a/packages/frontend/src/components/MkMiniChart.vue b/packages/frontend/src/components/MkMiniChart.vue
index 89050e10f0..e884455709 100644
--- a/packages/frontend/src/components/MkMiniChart.vue
+++ b/packages/frontend/src/components/MkMiniChart.vue
@@ -59,8 +59,8 @@ function draw(): void {
 
 	polygonPoints = `0,${ viewBoxY } ${ polylinePoints } ${ viewBoxX },${ viewBoxY }`;
 
-	headX = _polylinePoints[_polylinePoints.length - 1][0];
-	headY = _polylinePoints[_polylinePoints.length - 1][1];
+	headX = _polylinePoints.at(-1)![0];
+	headY = _polylinePoints.at(-1)![1];
 }
 
 watch(() => props.src, draw, { immediate: true });
diff --git a/packages/frontend/src/components/MkPageWindow.vue b/packages/frontend/src/components/MkPageWindow.vue
index 6318a9fd70..6e35ad4241 100644
--- a/packages/frontend/src/components/MkPageWindow.vue
+++ b/packages/frontend/src/components/MkPageWindow.vue
@@ -120,7 +120,7 @@ const contextmenu = $computed(() => ([{
 
 function back() {
 	history.pop();
-	router.replace(history[history.length - 1].path, history[history.length - 1].key);
+	router.replace(history.at(-1)!.path, history.at(-1)!.key);
 }
 
 function reload() {
diff --git a/packages/frontend/src/components/MkPagination.vue b/packages/frontend/src/components/MkPagination.vue
index 661b04c365..b9a75f6002 100644
--- a/packages/frontend/src/components/MkPagination.vue
+++ b/packages/frontend/src/components/MkPagination.vue
@@ -233,7 +233,7 @@ const fetchMore = async (): Promise<void> => {
 		...(props.pagination.offsetMode ? {
 			offset: offset.value,
 		} : {
-			untilId: Array.from(items.value.keys())[items.value.size - 1],
+			untilId: Array.from(items.value.keys()).at(-1),
 		}),
 	}).then(res => {
 		for (let i = 0; i < res.length; i++) {
@@ -297,7 +297,7 @@ const fetchMoreAhead = async (): Promise<void> => {
 		...(props.pagination.offsetMode ? {
 			offset: offset.value,
 		} : {
-			sinceId: Array.from(items.value.keys())[items.value.size - 1],
+			sinceId: Array.from(items.value.keys()).at(-1),
 		}),
 	}).then(res => {
 		if (res.length === 0) {
diff --git a/packages/frontend/src/scripts/array.ts b/packages/frontend/src/scripts/array.ts
index 4620c8b735..c9a146e707 100644
--- a/packages/frontend/src/scripts/array.ts
+++ b/packages/frontend/src/scripts/array.ts
@@ -78,8 +78,9 @@ 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/frontend/src/widgets/server-metric/cpu-mem.vue b/packages/frontend/src/widgets/server-metric/cpu-mem.vue
index c178ba5171..b9ba400b4d 100644
--- a/packages/frontend/src/widgets/server-metric/cpu-mem.vue
+++ b/packages/frontend/src/widgets/server-metric/cpu-mem.vue
@@ -121,10 +121,10 @@ function onStats(connStats) {
 	cpuPolygonPoints = `${viewBoxX - (stats.length - 1)},${viewBoxY} ${cpuPolylinePoints} ${viewBoxX},${viewBoxY}`;
 	memPolygonPoints = `${viewBoxX - (stats.length - 1)},${viewBoxY} ${memPolylinePoints} ${viewBoxX},${viewBoxY}`;
 
-	cpuHeadX = cpuPolylinePointsStats[cpuPolylinePointsStats.length - 1][0];
-	cpuHeadY = cpuPolylinePointsStats[cpuPolylinePointsStats.length - 1][1];
-	memHeadX = memPolylinePointsStats[memPolylinePointsStats.length - 1][0];
-	memHeadY = memPolylinePointsStats[memPolylinePointsStats.length - 1][1];
+	cpuHeadX = cpuPolylinePointsStats.at(-1)![0];
+	cpuHeadY = cpuPolylinePointsStats.at(-1)![1];
+	memHeadX = memPolylinePointsStats.at(-1)![0];
+	memHeadY = memPolylinePointsStats.at(-1)![1];
 
 	cpuP = (connStats.cpu * 100).toFixed(0);
 	memP = (connStats.mem.active / props.meta.mem.total * 100).toFixed(0);
diff --git a/packages/frontend/src/widgets/server-metric/net.vue b/packages/frontend/src/widgets/server-metric/net.vue
index 5a9134078d..817a422e63 100644
--- a/packages/frontend/src/widgets/server-metric/net.vue
+++ b/packages/frontend/src/widgets/server-metric/net.vue
@@ -94,10 +94,10 @@ function onStats(connStats) {
 	inPolygonPoints = `${viewBoxX - (stats.length - 1)},${viewBoxY} ${inPolylinePoints} ${viewBoxX},${viewBoxY}`;
 	outPolygonPoints = `${viewBoxX - (stats.length - 1)},${viewBoxY} ${outPolylinePoints} ${viewBoxX},${viewBoxY}`;
 
-	inHeadX = inPolylinePointsStats[inPolylinePointsStats.length - 1][0];
-	inHeadY = inPolylinePointsStats[inPolylinePointsStats.length - 1][1];
-	outHeadX = outPolylinePointsStats[outPolylinePointsStats.length - 1][0];
-	outHeadY = outPolylinePointsStats[outPolylinePointsStats.length - 1][1];
+	inHeadX = inPolylinePointsStats.at(-1)![0];
+	inHeadY = inPolylinePointsStats.at(-1)![1];
+	outHeadX = outPolylinePointsStats.at(-1)![0];
+	outHeadY = outPolylinePointsStats.at(-1)![1];
 
 	inRecent = connStats.net.rx;
 	outRecent = connStats.net.tx;