HTML5 WebSQL四种基本操作的介绍

nbsp;html&gt;    <script>    var end;    function setupDB() {        return this.createDatabase().then(createTable).then(insertEntry).then(readEntry).then(printResult);    }    function createTable() {        return new Promise(function(resovle, reject) {            console.log("prepare to create table..." + Date.now());            this._db.transaction(function(query) {                query.executeSql(&#39;create table if not exists user(id unique, user, passwd)&#39;);            });            setTimeout(_createTableOK.bind(this, resovle), 1000);        });    }    function _createTableOK(resovle) {        console.log("table created successfully..." + Date.now());        resovle();    }    function createDatabase() {        return new Promise(function(resovle, reject) {           console.log("prepare to create database..." + Date.now());            this._db = openDatabase(&#39;mydb&#39;, &#39;1.0&#39;, &#39;JerryTestdb&#39;, 1024);            setTimeout(_createDatabaseOK.bind(this, resovle), 1000);        });    }    function _createDatabaseOK(resovle) {        console.log("database created successfully..." + Date.now());        resovle(this._db);    }    function insertEntry() {        return new Promise(function(resolve, reject) {            this._db.transaction(function(query) {                query.executeSql("insert into user values (1,&#39;Jerry&#39;,&#39;1234&#39;)");            });            setTimeout(_insertEntryOK.bind(this, resolve), 1000);        });    }    function _insertEntryOK(resolve) {        console.log("entry inserted to table successfully..." + Date.now());        resolve();    }    function readEntry() {        return new Promise(function(resolve, reject) {            this._db.transaction(function(query) {                    query.executeSql(&#39;select * from user&#39;, [], function(u, results) {                        setTimeout(_readEntryOK.bind(this, resolve, results), 1000);                    }); // end of query.executeSql                } // end of function(query)           ); // end of this._db.transaction        });    }    function _readEntryOK(resolve, oResult) {        console.log("entry readed from DB successfully..." + Date.now());        resolve(oResult);    }    function printResult(oResults) {        for (var i = 0; i < oResults.rows.length; i++) {            document.writeln(&#39;id: &#39; + oResults.rows[i].id);            document.writeln(&#39;user: &#39; + oResults.rows[i].user);            document.writeln(&#39;passwd: &#39; + oResults.rows[i].passwd);        }        end = true;    }    function work() {        if (end) {            clearInterval(handle);        } else {            console.log(" working..." + Date.now());        }    }    setupDB();    var handle = setInterval(work, 200);    </script>