Question

我是JavaScript的新手，正在制作一个由注册表组成的餐厅应用程序。我想检查用户名是否已经存在，如果它确实存在，它应该在按钮点击时向用户发出警报。

JavaScript代码：

<script type="text/javascript">
var db;
var shortname="R_loginDB";
var version = "1.0";
var displayName = "R_loginDB";
var maxSize = 90000;

function onBodyLoad() {
    db = openDatabase(shortname,version,displayName,maxSize);
    db.transaction(function(tx){
        tx.executeSql('CREATE TABLE IF NOT EXISTS R(UserName TEXT NOT NULL PRIMARY KEY,Password TEXT NOT NULL,ConPassword TEXT NOT NULL)');
    });
}

function ListDBValues() {
    if (!window.openDatabase) {
        alert('Databases are not supported in this browser.');
        return;
    }

    $('#output').html('');

    db.transaction(function(transaction) {
        transaction.executeSql('SELECT * FROM R;', [], function(transaction, result) {
            if (result != null && result.rows != null) {
                for (var i = 0; i < result.rows.length; i++) {
                    var row = result.rows.item(i);
                    $('#output').append('<br>' +  ' ' + row.UserName+ ' ' + row.Password + ' '+ row.ConPassword);
                }
            }
        });
    });

    return;
}

ListDBValues();

function AddValues() {
    var flag = false;
    if ($("#pass").val() != $("#conpass").val()) {
        alert("Passwords do not match.");
        window.location.href = "r_register.html";
    } else if (flag == false) {
        try {
            db.transaction(function(transaction) {
                transaction.executeSql('INSERT INTO R(UserName, Password, ConPassword) VALUES (?,?,?)',[$('#uname').val(),$('#pass').val(),$('#conpass').val()]);
            });
            flag = true;
            window.location.href = "login.html";
        } catch(err) {
            alert("Username " + $("#uname").val() + " is already taken!! Please chose another one");
            window.location.href = "r_register.html";
        }
    }
}

AddValues();
</script>

HTML code：

<body onload="onBodyLoad()">
<div id="main">
    <img id="bg" src="file:///android_asset/www/images/bigtable_1_blur.jpg"/>

    <input id="uname" type="text" placeholder="    Username"></input>
    <input id="pass" type="password" placeholder="    Password"></input>
    <input id="conpass" type="password" placeholder="    Confirm Password"></input>
    <a href="login.html"><p id="login"><b>Already have an account?<i><u>Login</u></i></b></p></a>

    <!-- <a href="second.html"> -->
    <input id="btn" type="button" value="Register" onclick="AddValues()"></input><br/>

    <!-- </a> --> 
    <input id="btn2" type="button" value="show"  onclick="ListDBValues()"/></input>

    <span id="output"></span>
</div>
</body>

Answer 1

WebSQL API已被删除。它不太可能在目前不支持它的平台上得到支持，并且可以从那些支持平台的平台上删除。

尝试使用localStorage。点击Cordova storage documentation

了解详情

使用JavaScript检查SQLite中是否已存在用户名

1 个答案: