1.前端缓存几种方式: cookie、localStorage、sessionStorage、indexedDB，下面详细介绍indexedDB
2.完整代码
class DBManager {
dbName: any = null;
version: any = null;
db: any = null;
/**
* 初始化数据库名、版本
* @param dbName
* @param version
*/
constructor(dbName: String, version: String | Number) {
this.dbName = dbName;
this.version = version;
this.db = null;
}
/**
* 打开数据库
* @param callback
* @returns
*/
openDB(storeName?: String, keyPath?: String, keys?: Array<any>) {
return new Promise((resolve, reject) => {
if (this.db) {
resolve(this.db);
} else {
const cmd = indexedDB.open(this.dbName, this.version);
cmd.onsuccess = (e: any) => {
this.db = e.target.result;
resolve(this.db);
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
cmd.onupgradeneeded = (e: any) => {
this.createStore(storeName, keyPath, keys);
};
}
});
}
/**
* 关闭数据库
*/
closeDB() {
if (this.db) {
this.db.close();
this.db = null;
}
}
/**
* 删除数据库
* @returns
*/
deleteDB() {
return new Promise((resolve, reject) => {
const cmd = indexedDB.deleteDatabase(this.dbName);
cmd.onsuccess = (e: any) => {
resolve("");
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
});
}
/**
* 创建对象仓库
* @param storeName
* @param keyPath
* @param keys
* @returns
*/
createStore(storeName?: String, keyPath?: String, keys?: Array<any>) {
return new Promise(async (resolve, reject) => {
if (this.db) {
const store = this.db.createObjectStore(storeName, {
keyPath: keyPath,
autoIncrement: true,
});
if (keys) {
keys.forEach((key: any) => {
store.createIndex(key, key, { unique: key === keyPath ? true : false });
});
}
resolve(this.db);
} else {
reject("数据库未打开createStore");
}
});
}
/**
* 增加数据
* @param storeName
* @param data
* @returns
*/
insert(storeName: String, data: any) {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readwrite");
const store = transaction.objectStore(storeName);
const cmd = store.add(data);
cmd.onsuccess = (e: any) => {
resolve(e.target.result);
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
/**
* 查询数据，默认根据主键查询
* @param storeName
* @param value
* @returns
*/
queryByKey(storeName: String, value: any) {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readonly");
const store = transaction.objectStore(storeName);
const cmd = store.get(value);
cmd.onsuccess = (e: any) => {
resolve(e.target.result);
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
/**
* 查询全部数据记录
* @param storeName
* @returns
*/
queryAll(storeName: String) {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readonly");
const store = transaction.objectStore(storeName);
const cmd = store.getAll();
cmd.onsuccess = (e: any) => {
resolve(e.target.result);
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
/**
* 通过游标查询,跟queryByIndex的区别是：游标查询可定义查询条件，比如年龄在18-24之间的数据
* @param storeName
* @param range 查询条件
* @param direction 排序顺序
* @returns
*/
queryByCursor(storeName: String, key?: String, range?: any, direction: String = "next") {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readonly");
const store = transaction.objectStore(storeName);
const index = key ? store.index(key) : "";
const cursor = range ? index.openCursor(range, direction) : store.openCursor();
const result: Array<any> = [];
cursor.onsuccess = (e: any) => {
const cursor = e.target.result;
if (cursor) {
result.push(cursor.value);
cursor.continue();
}
resolve(result);
};
cursor.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
/**
* 通过键值对查询
* @param storeName
* @param indexName
* @param value
* @returns 获取：键为indexName，值为value 的那条数据
*/
queryByIndex(storeName: String, indexName: String, value: any) {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readonly");
const store = transaction.objectStore(storeName);
const cmd = store.index(indexName).get(value);
cmd.onsuccess = (e: any) => {
resolve(e.target.result);
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
/**
* 更新数据
* @param storeName
* @param key
* @param data
* @returns
*/
update(storeName: String, key: String, newData: any) {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readwrite");
const store = transaction.objectStore(storeName);
const cmd = store.get(key);
cmd.onsuccess = (e: any) => {
let data = e.target.result;
Object.assign(data, newData);
const requestUpdate = store.put(data);
requestUpdate.onsuccess = (e: any) => {
resolve(e.target.result);
};
requestUpdate.onerror = (e: any) => {
reject(e.target.error);
};
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
/**
* 删除数据
* @param storeName
* @param key
* @returns
*/
delete(storeName: String, key: String) {
return new Promise((resolve, reject) => {
if (this.db) {
const transaction = this.db.transaction(storeName, "readwrite");
const store = transaction.objectStore(storeName);
const cmd = store.delete(key);
cmd.onsuccess = (e: any) => {
resolve(e.target.result);
};
cmd.onerror = (e: any) => {
reject(e.target.error);
};
} else {
reject("数据库未打开");
}
});
}
}
export default DBManager;
3.在项目中使用
template:
<button @click="learnDb('open')">打开</button>
<button @click="learnDb('add')">添加</button>
<button @click="learnDb('search')">查询</button>
<button @click="learnDb('delete')">删除</button>
<button @click="learnDb('update')">更新</button>
<button @click="learnDb('close')">关闭</button>
<button @click="learnDb('clearn')">清除</button>
script:
//学习indexedDB
let myDB = new DBManager("zhengjie", 1);
let learnDb = async (type: String) => {
if (type == "clearn") {
myDB.deleteDB();
} else if (type == "open") {
myDB.openDB("users", "name", ["name", "age"]);
} else if (type == "add") {
myDB.insert("users", { name: "整洁", age: 18 });
} else if (type == "search") {
// let a = await myDB.queryByKey("users", "整洁");
// let a = await myDB.queryAll("users");
// const range = IDBKeyRange.only(24);
// let a = await myDB.queryByCursor("users", "age", range); //查询名字(name)为整洁的数据
let a = await myDB.queryByIndex("users", "age", 24);
console.log("查找数据", a);
} else if (type == "delete") {
myDB.delete("users", "整洁");
} else if (type == "update") {
myDB.update("users", "整洁", { name: "整洁", age: 24 });
} else if (type == "close") {
myDB.closeDB();
}
};