IndexedDBStorage

2025年01月19日

柏拉文

越努力，越幸运

一、认识

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IndexedDBStorage 用于与 LocalStorage 一样的功能: 支持有效期, 数据存储时可以设置有效期（以毫秒为单位）; 存储：记录过期时间戳; 读取：检查时间戳，过期则返回 null 并删除数据; 懒删除: 过期数据仅在读取时被清理，避免对性能产生影响; 保持标准 API, 提供 setItem、getItem、removeItem、clear、keys 等方法，接口清晰且易于使用; 而且支持大容量存储: 依托 IndexedDB 的优势，支持存储更大规模的数据，同时具备结构化存储能力。不过, IndexedDB 的存储是异步存储, LocalStorage 是同步的。

二、实现

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class EnhancedIndexedDBStorage {
    constructor(dbName = 'appDB', storeName = 'keyValueStore') {
        this.dbName = dbName;       // 数据库名称
        this.storeName = storeName; // 存储对象名称
        this.dbPromise = this.initDB();
    }

    // 初始化数据库
    initDB() {
        return new Promise((resolve, reject) => {
            const request = indexedDB.open(this.dbName, 1);
            request.onupgradeneeded = (event) => {
                const db = event.target.result;
                if (!db.objectStoreNames.contains(this.storeName)) {
                    db.createObjectStore(this.storeName, { keyPath: 'key' }); // 创建存储对象
                }
            };
            request.onsuccess = (event) => resolve(event.target.result);
            request.onerror = (event) => reject(event.target.error);
        });
    }

    // 获取存储对象
    async getStore(mode = 'readonly') {
        const db = await this.dbPromise;
        const transaction = db.transaction(this.storeName, mode);
        return transaction.objectStore(this.storeName);
    }

    /**
     * 设置数据，支持有效期
     * @param {string} key 键名
     * @param {*} value 要存储的值
     * @param {number} expiry 有效期（毫秒），可选
     */
    async setItem(key, value, expiry = null) {
        const store = await this.getStore('readwrite');
        const data = {
            value,
            expiry: expiry ? Date.now() + expiry : null, // 计算过期时间
        };
        return new Promise((resolve, reject) => {
            const request = store.put({ key, ...data });
            request.onsuccess = () => resolve();
            request.onerror = (event) => reject(event.target.error);
        });
    }

    /**
     * 获取数据，检查有效期
     * @param {string} key 键名
     * @returns {*} 数据或 null（如果过期或不存在）
     */
    async getItem(key) {
        const store = await this.getStore();
        return new Promise((resolve, reject) => {
            const request = store.get(key);
            request.onsuccess = (event) => {
                const result = event.target.result;
                if (!result) {
                    resolve(null);
                    return;
                }
                const { value, expiry } = result;
                if (expiry && Date.now() > expiry) {
                    // 数据过期，删除该项
                    this.removeItem(key);
                    resolve(null);
                } else {
                    resolve(value);
                }
            };
            request.onerror = (event) => reject(event.target.error);
        });
    }

    /**
     * 删除数据
     * @param {string} key 键名
     */
    async removeItem(key) {
        const store = await this.getStore('readwrite');
        return new Promise((resolve, reject) => {
            const request = store.delete(key);
            request.onsuccess = () => resolve();
            request.onerror = (event) => reject(event.target.error);
        });
    }

    /**
     * 清空所有数据
     */
    async clear() {
        const store = await this.getStore('readwrite');
        return new Promise((resolve, reject) => {
            const request = store.clear();
            request.onsuccess = () => resolve();
            request.onerror = (event) => reject(event.target.error);
        });
    }

    /**
     * 获取所有键
     * @returns {Promise<string[]>} 所有键的数组
     */
    async keys() {
        const store = await this.getStore();
        return new Promise((resolve, reject) => {
            const request = store.getAllKeys();
            request.onsuccess = (event) => resolve(event.target.result);
            request.onerror = (event) => reject(event.target.error);
        });
    }

    /**
     * 获取键值对数量
     * @returns {Promise<number>} 键值对数量
     */
    async length() {
        const keys = await this.keys();
        return keys.length;
    }
}

// 示例用法
(async () => {
    const storage = new EnhancedIndexedDBStorage('myAppDB', 'myStore');

    // 设置值，5 秒后过期
    await storage.setItem('user', { name: 'Alice', age: 30 }, 5000);
    await storage.setItem('token', 'abcdef', 10000);

    // 立即读取
    console.log(await storage.getItem('user')); // { name: 'Alice', age: 30 }

    // 6 秒后读取
    setTimeout(async () => {
        console.log(await storage.getItem('user')); // null（过期自动清理）
        console.log(await storage.getItem('token')); // 'abcdef'
    }, 6000);

    // 清空存储
    await storage.clear();
    console.log(await storage.keys()); // []
})();