你也可以用JQuery动态地做到这一点

设置所需的

$("#select1").attr('required', 'required');

删除需要

$("#select1").removeAttr('required');

你也可以用JQuery动态地做到这一点

设置所需的

$("#select1").attr('required', 'required');

删除需要

$("#select1").removeAttr('required');

你需要将option的value属性设置为空字符串:

<select name="status" required>
    <option selected disabled value="">what's your status?</option>
    <option value="code">coding</option>
    <option value="sleep">sleeping</option>
</select>

当用户在表单上按submit键时，Select将向服务器返回所选选项的值。空值与空文本输入相同——>引发所需的消息。

w3schools

value属性指定提交表单时发送到服务器的值。 例子

<select>元素支持required属性，按照规范:

http://dev.w3.org/html5/spec-author-view/the-select-element.html#the-select-element

哪个浏览器不支持这个功能?

(当然，无论如何您都必须在服务器上验证，因为您不能保证用户将启用JavaScript。)

<form action="">

<select required>

  <option selected disabled value="">choose</option>
  <option value="red">red</option>
  <option value="yellow">yellow</option>
  <option value="green">green</option>
  <option value="grey">grey</option>

</select>
<input type="submit">
</form>

必填项:第一个值为空-必填项工作为空值

先决条件:正确的html5 DOCTYPE和命名输入字段

<select name="somename" required>
<option value="">Please select</option>
<option value="one">One</option>
</select>

根据文档(列表和粗体是我的)

The required attribute is a boolean attribute. When specified, the user will be required to select a value before submitting the form. If a select element has a required attribute specified, does not have a multiple attribute specified, and has a display size of 1 (do not have SIZE=2 or more - omit it if not needed); and if the value of the first option element in the select element's list of options (if any) is the empty string (i.e. present as value=""), and that option element's parent node is the select element (and not an optgroup element), then that option is the select element's placeholder label option.