openDatabase database web front-end cache (code example)

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This database caching api learning requires some basic knowledge of database operation statements. If you don’t understand the simple addition, deletion, checking and modification of database statements, it is recommended that children’s shoes who watch this blog first go to XiaoxiaoLearn about the addition, deletion, modification and query of database statements. This article is only an example demonstration of the basic operations of add, delete, modify and query of the database table. It does not do some related operations of the database table, but Meet most of everyone's requirements for front-end data caching.

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    <meta>
    <title>Title</title>



<!--
openDatabase与android里面的sqlite差不多
最好的选型存储
-->

<h1 id="opendatabse数据库操作">opendatabse数据库操作</h1>

<button>创建user数据表</button>
<button>插入数据</button>
<button>查询数据</button>
<button>修改数据</button>
<button>删除数据</button>
<button>删除user数据表</button>

<script>

    let findId = id => document.getElementById(id);

    //模拟一条user数据
    let user = {
        username: "liuqiang",
        password: "123569874",
        info: "beaconApp开发团队中一员"
    };

    /**
     * 创建数据库 或者此数据库已经存在 那么就是打开数据库
     * name: 数据库名称
     * version: 版本号
     * displayName: 对数据库的描述
     * estimatedSize: 设置数据的大小
     * creationCallback: 回调函数(可省略)
     */
    let db = openDatabase("MySql", "1.0", "我的数据库描述", 1024 * 1024);
    let result = db ? "数据库创建成功" : "数据库创建失败";
    console.log(result);


    const USER_TABLE_SQL = "create table if not exists userTable (id integer primary key autoincrement,username varchar(12)," +
        "password varchar(16),info text)";

    //创建数据表
    function createTable() {
        db.transaction(tx => {
            tx.executeSql(USER_TABLE_SQL, [],
                (tx, result) => {
                    alert(&#39;创建user表成功:&#39; + result);
                }, (tx, error) => {
                    alert(&#39;创建user表失败:&#39; + error.message);
                })
        })
    }

    const INSERT_USER_SQL = "insert into userTable (username, password,info) values(?,?,?)";

    //插入数据
    function insertData(user) {
        db.transaction(tx => {
            tx.executeSql(INSERT_USER_SQL,
                [user.username, user.password, user.info],
                (tx, result) => {
                    alert(&#39;添加数据成功:&#39;);
                }, (tx, error) => {
                    alert(&#39;添加数据失败:&#39; + error.message);
                })
        })
    }

    const QUERY_USER_SQL = "select * from userTable";

    //查询数据
    function queryData() {
        db.transaction(tx => {
            tx.executeSql(QUERY_USER_SQL, [],
                (tx, result) => {
                    console.log(result);
                },
                (tx, error) => {
                    console.log(&#39;查询失败: &#39; + error.message)
                })
        })
    }

    const UPDATE_USER_SQL = "update userTable set password = ? where username = ?";

    //修改数据
    function updateData(user) {
        db.transaction(tx => {
            tx.executeSql(UPDATE_USER_SQL, [user.password, user.username],
                (tx, result) => {
                    alert("修改数据成功")
                }, (tx, error) => {
                    alert("修改数据失败:" + error.message)
                })
        })
    }

    const DELETE_USER_SQL = "delete from userTable where username = ?";

    //删除数据
    function deleteData(user) {
        db.transaction(tx => {
            tx.executeSql(DELETE_USER_SQL, [user.username],
                (transaction, resultSet) => {
                    alert("删除数据成功")
                }, (transaction, error) => {
                    alert("删除数据失败:" + error.message)
                })
        });
    }

    const DROP_USER_SQL = "drop table userTable";

    //删除数据表
    function dropTable() {
        db.transaction(tx => {
            tx.executeSql(DROP_USER_SQL, [],
                (transaction, resultSet) => {
                    alert("删除数据表成功")
                }, (transaction, error) => {
                    alert("删除数据表失败:" + error.message)
                })
        })
    }

    /**
     * 点击事件 增删查改
     */
    let btnCreate = findId("btn-create");
    let btnInsert = findId("btn-insert");
    let btnQuery = findId("btn-query");
    let btnUpdate = findId("btn-update");
    let btnDelete = findId("btn-delete");
    let btnDrop = findId("btn-drop");
    btnCreate.onclick = () => createTable();
    btnInsert.onclick = () => insertData(user);
    btnQuery.onclick = () => queryData();
    btnUpdate.onclick = () => {
        user.password = "111666666"; //修改密码
        updateData(user);
    };
    btnDelete.onclick = () => deleteData(user);
    btnDrop.onclick = () => dropTable();

</script>

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