required
placeholder
autofocus
autocomplete
<optgroup label="北京">
<option>东城区</option>
<option>西城区</option>
<option>海淀区</option>
</optgroup>
<optgroup label="成都">
<option>青羊区</option>
<option>金牛区</option>
<option>金牛区</option>
</optgroup>
<input type="text" list="cars">
<datalist id="cars">
<option>宝马<option>
<option>大众<option>
<option>奥迪<option>
</datalist>
mark
