rt，我写了这样一段代码

但是放入侧边栏html代码的时候发现不能实现函数调用

请问可以怎么解决呢？

<!DOCTYPE html>
<html>
<head>
    <style type = "text/css"> 
    </style>
    <title> 事件</title>
    <script type="text/javascript">
        function jump() {
            var opt = document.getElementById("select").value;
            var id = document.getElementById("txt2").value;
            var luogulink = "https://www.luogu.org/problemnew/show/P",
                bzojlink  = "https://www.lydsy.com/JudgeOnline/problem.php?id=",
                lojlink   = "https://loj.ac/problem/";
            if(opt == 'luogu') {
                window.open(luogulink + id);
            } else if(opt == 'bzoj') {
                window.open(bzojlink + id);
            } else if(opt == 'loj') {
                window.open(lojlink + id);
            }
        }
        function erase() {
            var a = document.getElementById("txt2");
            a.value = "";
        }
    </script>
</head>

<body>
    <span>请选择OJ</sapn>
    <select id='select'>
        <option value = 'luogu'>洛谷</option>
        <option value = 'bzoj'>bzoj</option>
        <option value = 'loj'> loj </option>
    </select>
    <input type='text' id='txt2' value='请输入题号' onfocus="erase()"/>
    <input type='button' value=' go ' onclick="jump()" />
    </br>
    <!--通过 = 按钮来调用创建的函数，得到结果-->
</body>

</html>