indexedDB笔记

笔记"/>

indexedDB笔记

indexedDB

该部分内容主要源于

• 常用场景：大量数据需要缓存在本地
• 重要概念
  • 仓库objectStore：类似于数据库中的表，数据存储媒介
  • 索引index：索引作为数据的标志量，可根据索引获取对应值
  • 游标cursor：数据的遍历工具

1.创建数据库

/*** 打开数据库* @param {string} dbName 数据库的名字* @param {string} storeName 仓库名称* @param {string} version 数据库的版本* @return {object} 返回一个数据库实例*/
function openDB(dbName, version = 1) {return new Promise((resolve, reject) => {var indexedDB =window.indexedDB ||window.mozIndexedDB ||window.webkitIndexedDB ||window.msIndexedDB;const request = indexedDB.open(dbName, version);// 数据库打开成功回调request.onsuccess = function (event) {let db = event.target.result;console.log("数据库打开成功");resolve(db);};// 数据库打开失败的回调request.onerror = function () {console.log("数据库打开报错");reject()};// 数据库创建或版本更新时触发request.onupgradeneeded = function (event) {console.log("onupgradeneeded");let db = event.target.result;// 创建仓库let objectStore = db.createObjectStore("store", {keyPath: "id", // 这是主键// autoIncrement: true // 实现自增});// 创建索引，在后面查询数据的时候可以根据索引查objectStore.createIndex("id", "id", {unique: false});};});
}

2.关闭数据库

/*** 关闭数据库* @param {object} db 数据库实例*/
function closeDB(db) {db.close();console.log("数据库已关闭");
}

3.删除数据库

/*** 删除数据库* @param {object} dbName 数据库名称*/
function deleteDB(dbName) {let deleteRequest = window.indexedDB.deleteDatabase(dbName);deleteRequest.onerror = function () {console.log("删除失败");};deleteRequest.onsuccess = function () {console.log("删除成功");};
}

4.新增数据

/*** 新增数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {object} data 数据（键值对格式，必须包含主键与索引字段）*/
function addData(db, storeName, data) {// 创建事务对象，指定表格名称和操作模式（"只读"或"读写"）let transaction = db.transaction([storeName], "readwrite")// 获取仓库对象let store = transaction.objectStore(storeName)// 执行插入操作let request = store.add(data)request.onsuccess = function () {console.log("数据写入成功");};request.onerror = function () {console.log("数据写入失败");};
}

5.更新数据

/*** 更新数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {object} data 数据*/
function updateData(db, storeName, data) {let transaction = db.transaction([storeName], "readwrite")let store = transaction.objectStore(storeName)let request = store.put(data); // 如果没有该数据则为新增request.onsuccess = function () {console.log("数据更新成功");};request.onerror = function () {console.log("数据更新失败");};
}

6.根据主键删除数据

/*** 通过主键删除数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {object} id 主键值*/
function delData(db, storeName, id) {let transaction = db.transaction([storeName], "readwrite")let store = transaction.objectStore(storeName)let request = store.delete(id)request.onsuccess = function () {console.log("数据删除成功");};request.onerror = function () {console.log("数据删除失败");};
}

7.根据索引值删除数据

/*** 通过索引和游标删除指定的数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {string} indexName 索引名* @param {object} indexValue 索引值*/
function cursorDelete(db, storeName, indexName, indexValue) {let transaction = db.transaction(storeName, "readwrite")let store = transaction.objectStore(storeName)let request = store.index(indexName).openCursor(IDBKeyRange.only(indexValue));request.onsuccess = function (e) {let cursor = e.target.result;let deleteRequest;if (cursor) {deleteRequest = cursor.delete(); // 请求删除当前项deleteRequest.onerror = function () {console.log("游标删除该记录失败");};deleteRequest.onsuccess = function () {console.log("游标删除该记录成功");};cursor.continue();}};request.onerror = function () {console.log('事务失败')};
}

8.通过游标获取全量数据

/*** 通过游标获取全量数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称*/
function getAllData(db, storeName) {return new Promise((resolve, reject) => {let list = []let transaction = db.transaction(storeName, "readwrite")let store = transaction.objectStore(storeName)let request = store.openCursor()// 游标开启成功，逐行读数据request.onsuccess = function (e) {let cursor = e.target.result// 必须要检查if (cursor) {list.push(cursor.value);cursor.continue(); // 遍历存储对象中的所有内容} else {console.log("游标读取的数据：", list);resolve(list)}};request.onerror = function () {console.log("事务失败");reject()};})
}

9.通过主键获取数据

/*** 通过主键获取数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {string} key 主键值（创建时声明的keypath字段）*/
function getDataByKey(db, storeName, key) {return new Promise((resolve, reject) => {var transaction = db.transaction([storeName]);var store = transaction.objectStore(storeName);var request = store.get(key);request.onsuccess = function () {// 仅查询一条数据console.log("主键查询结果: ", request.result);resolve(request.result);};request.onerror = function () {console.log("事务失败");reject()};});
}

10.通过索引获取数据

/*** 通过索引获取数据* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {string} indexName 索引名称* @param {string} indexValue 索引值*/
function getDataByIndex(db, storeName, indexName, indexValue) {return new Promise((resolve, reject) => {let transaction = db.transaction(storeName, "readwrite")let store = transaction.objectStore(storeName)let request = store.index(indexName).get(indexValue)request.onsuccess = function (e) {// 所有符合索引值的数据let result = e.target.resultconsole.log("索引查询结果：", result)resolve(result)};request.onerror = function () {console.log("事务失败")reject()};})
}

11.通过索引与游标结合筛选数据

/*** 通过索引和游标查询记录* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {string} indexName 索引名称* @param {string} indexValue 索引值*/
function cursorGetDataByIndex(db, storeName, indexName, indexValue) {return new Promise((resolve, reject) => {let list = []let transaction = db.transaction(storeName, "readwrite")let store = transaction.objectStore(storeName);let request = store.index(indexName).openCursor(IDBKeyRange.only(indexValue))request.onsuccess = function (e) {let cursor = e.target.resultif (cursor) {// 区别于根据索引获取数据，此处可引入筛选相关逻辑list.push(cursor.value);cursor.continue();} else {console.log("游标索引查询结果：", list);resolve(list)}};request.onerror = function () {console.log("事务失败")reject()};})
}

12.通过索引和游标分页查询

/*** 通过索引和游标分页查询记录* @param {object} db 数据库实例* @param {string} storeName 仓库名称* @param {string} indexName 索引名称* @param {string} indexValue 索引值* @param {number} page 页码* @param {number} pageSize 查询条数*/
function cursorGetDataByIndexAndPage(db,storeName,indexName,indexValue,page,pageSize
) {return new Promise((resolve, reject) => {let list = [];let counter = 0; // 计数器let advanced = true; // 是否跳过多少条查询let transaction = db.transaction(storeName, "readwrite")let store = transaction.objectStore(storeName)var request = store.index(indexName).openCursor(IDBKeyRange.only(indexValue))request.onsuccess = function (e) {var cursor = e.target.result;if (page > 1 && advanced) {advanced = false;cursor.advance((page - 1) * pageSize); // 跳过多少条return;}if (cursor) {list.push(cursor.value);counter++;if (counter < pageSize) cursor.continue()else {cursor = null;console.log("分页查询结果", list);}} else {console.log("分页查询结果", list);resolve(list)}};request.onerror = function () {console.log("事务失败");reject()};})
}