如何实现浮动窗口效果的JavaScript代码是什么？

浮动窗口（Floating Window）是一种在网页上显示的可拖动、可调整大小的弹出窗口，它通常用于提供额外的信息或功能，而不会干扰用户对主页面内容的查看。

以下是一个简单的JavaScript代码示例，用于创建一个基本的浮动窗口：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>浮动窗口示例</title>
    <style>
        #floatingWindow {
            width: 300px;
            height: 200px;
            position: fixed;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background-color: white;
            border: 1px solid #ccc;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
            z-index: 1000;
            display: none;
        }
        #floatingWindowHeader {
            padding: 10px;
            background-color: #f1f1f1;
            cursor: move;
        }
        #floatingWindowContent {
            padding: 10px;
        }
        #overlay {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            z-index: 999;
            display: none;
        }
    </style>
</head>
<body>
    <button onclick="showFloatingWindow()">打开浮动窗口</button>
    <div id="overlay"></div>
    <div id="floatingWindow">
        <div id="floatingWindowHeader">浮动窗口</div>
        <div id="floatingWindowContent">
            <p>这是一个浮动窗口的内容。</p>
            <button onclick="hideFloatingWindow()">关闭</button>
        </div>
    </div>
    <script>
        function showFloatingWindow() {
            document.getElementById('overlay').style.display = 'block';
            document.getElementById('floatingWindow').style.display = 'block';
        }
        function hideFloatingWindow() {
            document.getElementById('overlay').style.display = 'none';
            document.getElementById('floatingWindow').style.display = 'none';
        }
        // 使浮动窗口可拖动
        let floatingWindow = document.getElementById('floatingWindow');
        let header = document.getElementById('floatingWindowHeader');
        let offsetX, offsetY;
        header.onmousedown = function(event) {
            offsetX = event.clientX floatingWindow.getBoundingClientRect().left;
            offsetY = event.clientY floatingWindow.getBoundingClientRect().top;
            document.onmousemove = function(event) {
                floatingWindow.style.left = (event.clientX offsetX) + 'px';
                floatingWindow.style.top = (event.clientY offsetY) + 'px';
            };
            document.onmouseup = function() {
                document.onmousemove = null;
                document.onmouseup = null;
            };
        };
    </script>
</body>
</html>