由于onbeforeunload事件的异步性质，在页面刷新或关闭时可靠地提交表单可能具有挑战性。
使用navigator.sendBeacon方法，该方法设计用于在后台发送数据，即使在页面卸载期间也是如此

<script>
    window.addEventListener('beforeunload', function (e) {
        document.getElementById("demo1").innerHTML = "No";

        // Serialize form data
        var formData = new FormData(document.getElementById("all_questions"));
        var data = new URLSearchParams(formData);

        // Send data using navigator.sendBeacon
        navigator.sendBeacon("/your-submit-endpoint", data);
    });

    // If you also want to handle form submission on button click
    document.getElementById("all_questions").addEventListener('submit', function (e) {
        e.preventDefault(); // Prevent the default form submission
        document.getElementById("demo1").innerHTML = "No";

        // Serialize form data
        var formData = new FormData(this);
        var data = new URLSearchParams(formData);

        // Send data using navigator.sendBeacon
        navigator.sendBeacon("/your-submit-endpoint", data);
        
        // Optionally, you can redirect or perform other actions after form submission
    });
</script>

<form method="POST" name="answer_question" id="all_questions">
    <p id="demo1">Yes</p>
    data
    <div class="save-item1"><button class="save-button" type="submit" id="save" name="Complete">Save</button></div>
</form>

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