纯js实现自定义模态框

     <div id="modal-overlay"> 
    <div class="modal-data">        
        <p>一个很简单的模态对话框 </p>
        <p>点击<a onclick="overlay()" href="/go.html?url=">这里</a>关闭</p>
    </div>
</div>

<a href="/go.html?url=#" onclick="overlay()">显示模态对话框</a>
        <style>     <div id="modal-overlay"> 
    <div cla