选择搜索引擎进行搜索

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>选择搜索引擎进行搜索</title>
    <script>
        function searchSelectedEngine() {
            var keyword = document.getElementById('keyword').value;
            var engine = document.getElementById('engine').value;
            var encodedKeyword = encodeURIComponent(keyword);

            var searchUrl;

            switch (engine) {
                case 'bing':
                    searchUrl = "https://www.bing.com/search?q=" + encodedKeyword;
                    break;
                case 'baidu':
                    searchUrl = "https://www.baidu.com/s?wd=" + encodedKeyword;
                    break;
                case 'sogou':
                    searchUrl = "https://www.sogou.com/web?query=" + encodedKeyword;
                    break;
                case 'so':
                    searchUrl = "https://www.so.com/s?q=" + encodedKeyword;
                    break;
                default:
                    alert("请选择一个搜索引擎。");
                    return;
            }

            window.open(searchUrl, "_blank");
        }
    </script>
</head>
<body>
    <h1>选择搜索引擎进行搜索</h1>
    <label for="keyword">输入关键词：</label>
    <input type="text" id="keyword" required>
    <label for="engine">选择搜索引擎：</label>
    <select id="engine">
        <option value="bing">Bing</option>
        <option value="baidu">Baidu</option>
        <option value="sogou">Sogou</option>
        <option value="so">So.com</option>
    </select>
    <button onclick="searchSelectedEngine()">搜索</button>
</body>
</html>