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Javascript 函数仅在页面刷新后有效

转载 作者：行者123 更新时间：2023-11-29 15:44:51 31 4
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如果我点击“发送”按钮，一条消息将被放入客户端 sql 数据库中并显示一条通知。

但是，这只有在我先刷新页面时才有效!

如何让函数立即开始工作？我已经尝试将函数“addMessage”放在 $(document).ready(function() 中，但随后该函数完全停止工作。请参见下面的代码:

<script>
        var db;

        $(document).ready(function()    {
            //Opens the database
            try
            {
              if (!window.openDatabase) {
                    alert('Not supported -> Please use a webkit browser');
              } else {
                  var shortName = 'Rvpk';
                  var version = '1.0';
                  var displayName = 'The Rvpk databse';
                  var maxSize = 3072*1024; //  = 3MB in bytes 65536
                  db = openDatabase(shortName, version, displayName, maxSize);      
                  }  
            }
            catch(e)
            {
              if (e == 2) {
                  alert("Invalid database version.");
              } else {
                  alert("Unknown error "+e+".");
              }return;
            }

            //If needed creates the messagetable
            db.transaction(function (tx) {
                 tx.executeSql('CREATE TABLE IF NOT EXISTS message (id INTEGER PRIMARY KEY, name)')                    
            });
        });

        //The function addMessage takes the entered message from the message inputfield and places it inside the messagetable
        function addMessage(){
        var message = $('input:text[name=message]').val();

            db.transaction(function (tx) {
                     tx.executeSql("INSERT INTO message (id, name) VALUES (NULL, ?)", [message]);
            });
            console.log("Message "+ message +" added to database");

            //Shows a notification that sending the message was a success
            alert('The message has been sent');

            //Update the messages
            updateMessages();            
        }    
    </script>
    </head>

    <body>
    <?php include("includes/header2.php"); ?>

                <div data-role="content">
                    <form>
                        <fieldset>
                            <label id="messagelabel" for="message">Message:</label>
                            <input id="message" type="text" name="message" value="This can't go on like this">
                            <button onClick="addMessage()" data-theme="g">Send</button>
                        </fieldset>
                    </form>
                </div>

最佳答案

请试试这个:

document.ready 仅在页面加载时运行。而是在单独的函数中使用它，并在需要时调用该函数。复制并粘贴以下脚本。

<script>
        var db;

        function runThis()
        {
            //Opens the database
            try
            {
              if (!window.openDatabase) {
                    alert('Not supported -> Please use a webkit browser');
              } else {
                  var shortName = 'Rvpk';
                  var version = '1.0';
                  var displayName = 'The Rvpk databse';
                  var maxSize = 3072*1024; //  = 3MB in bytes 65536
                  db = openDatabase(shortName, version, displayName, maxSize);      
                  }  
            }
            catch(e)
            {
              if (e == 2) {
                  alert("Invalid database version.");
              } else {
                  alert("Unknown error "+e+".");
              }return;
            }

            //If needed creates the messagetable
            db.transaction(function (tx) {
                 tx.executeSql('CREATE TABLE IF NOT EXISTS message (id INTEGER PRIMARY KEY, name)')                    
            });
        }

        //The function addMessage takes the entered message from the message inputfield and places it inside the messagetable
        function addMessage(){

        //call db access function.
        runThis();

        var message = $('input:text[name=message]').val();

            db.transaction(function (tx) {
                     tx.executeSql("INSERT INTO message (id, name) VALUES (NULL, ?)", [message]);
            });
            console.log("Message "+ message +" added to database");

            //Shows a notification that sending the message was a success
            alert('The message has been sent');

            //Update the messages
            updateMessages();            
        }    
    </script>

关于Javascript 函数仅在页面刷新后有效，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13208305/

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