思路:利用CSS僞類,爲select添加僞類required,即不能爲空;而默認選項(Placeholder)的value爲空,觸發invalid,實現不選時置灰的效果;
Demo:
<style>
select:invalid { color: gray; }
</style>
<select required>
<option value="" disabled selected hidden>Select your option</option>
<option value="M">Male</option>
<option value="F">Female</option>
</select>
效果如下:
兼容性:
Chrome,FF 完美實現
Safari,IE11,Edge(下拉列表中可見palceholder,但是不能選)
低版本IE待驗證