1 files changed, 57 insertions, 0 deletions
diff --git a/packages/frontend/src/memory-storage.ts b/packages/frontend/src/memory-storage.ts
new file mode 100644
index 0000000000..df0dc1308f
--- /dev/null
+++ b/packages/frontend/src/memory-storage.ts
@@ -0,0 +1,57 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export type MemoryStorage = {
+	has: (key: string) => boolean;
+	getItem: <T>(key: string) => T | null;
+	setItem: (key: string, value: unknown) => void;
+	removeItem: (key: string) => void;
+	clear: () => void;
+	size: number;
+};
+
+class MemoryStorageImpl implements MemoryStorage {
+	private readonly storage: Map<string, unknown>;
+
+	constructor() {
+		this.storage = new Map();
+	}
+
+	has(key: string): boolean {
+		return this.storage.has(key);
+	}
+
+	getItem<T>(key: string): T | null {
+		return this.storage.has(key) ? this.storage.get(key) as T : null;
+	}
+
+	setItem(key: string, value: unknown): void {
+		this.storage.set(key, value);
+	}
+
+	removeItem(key: string): void {
+		this.storage.delete(key);
+	}
+
+	clear(): void {
+		this.storage.clear();
+	}
+
+	get size(): number {
+		return this.storage.size;
+	}
+}
+
+export function createMemoryStorage(): MemoryStorage {
+	return new MemoryStorageImpl();
+}
+
+/**
+ * SessionStorageよりも更に短い期間でクリアされるストレージです
+ * - ブラウザの再読み込みやタブの閉じると内容が揮発します
+ * - このストレージは他のタブと共有されません
+ * - アカウント切り替えやログアウトを行うと内容が揮発します
+ */
+export const defaultMemoryStorage: MemoryStorage = createMemoryStorage();