为啥将placeholder属性换成value属性下拉选项就无法出现

来源：3-18 编程练习

努力变强ing

2019-03-26 21:20:15

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>datalist</title>
</head>
<body>
   
   <input placeholder="请选择学习的语言" list="lange"/>
   <datalist id="lange">
       <option value="JAVA">JAVA</option>
       <option value="c++">c++</option>
       <option value="JavaScript">JavaScript</option>
       <option value=".NET">.NET</option>
       <option value="C#">c#</option>
   </datalist>
</body>
</html>