select控件变成可输入状态

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
 <meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
 <style type="text/css">
    .boxBg{
        position:relative;
        width:200px;
        height:20px;
        margin:0 auto

    }
    .sBox{
        width:200px;
        height:20px;
    
    }
    .inputBox{
        position:absolute;
        left:0;
        top:0;
        width:179px;
        height:16px;
        border:1px solid green;
    }
 </style>
 

  <script type="text/javascript">
    function myselect(value){
    var element = document.getElementById('inputBox');
        if(value == 0){
            element.style.display = "block";
        }else{
            element.style.display = "none";
        }
    }
    
  </script>
 <title>3D标签-柯乐义</title>
</head>
<body>
    <div class="boxBg">
        <select id="sValue" class="sBox" onchange="myselect(this.value);">
            <option value="0">请输入</option>
            <option value="1">星期一</option>
            <option value="2">星期二</option>
            <option value="3">星期三</option>
            <option value="4">星期四</option>
            <option value="5">星期五</option>
            <option value="6">星期六</option>
            <option value="7">星期天</option>
        </select>
        <input type="text" value="请输入" class="inputBox" id="inputBox"/>
    </div>
</body>
</html>
执行结果：
当选择输入时，可以手动输入。