道歉,这看起来非常基本.我试图在输入字段中显示下拉列表的值.我一直在戳它几个小时,不能弄清楚我做错了什么.
function myFunction(){
var e = document.getElementById("theDay");
var dayValue = e.options[e.selectedIndex].value;
document.getElementById("formValue").value = dayValue;
}<!DOCTYPE html>
<html lang="en">
<body>
<form action="" name="theForm">
<select name="theDay" size="7">
<option value="0">Monday</option>
<option value="1">Tuesday</option>
<option value="2">Wednesday</option>
<option value="3">Thursday</option>
<option value="4">Friday</option>
<option value="5">Saturday</option>
<option value="6">Sunday</option>
</select>
</form>
<button onclick="myFunction()">Click me</button>
to show drop down value <input type="text" id="formValue">
</body>
</html>