6.1.7 forms.base.select Select list
The <select> element represents a form field for selecting amongst a set of
options.
Known limitation: by default, Chrome and Safari on OS X allow very limited
styling of <select>, unless a border property is set.
For most Drupal-based GNWT websites, the select element is replaced with the
chosen module, negating any required styling.
Example
Markup: base/forms/forms-select.twig
<div>
<label for="selectDropdown">A standard drop-down</label>
<select class="{{modifier_class}}" id="selectDropdown">
<option>Option 1</option>
<option>Option 2</option>
<option>Option 3</option>
<optgroup label="More options">
<option>Option 4</option>
<option>Option 5</option>
</optgroup>
</select>
</div>
<div>
<label for="selectMultiItem">A multi-item select field</label>
<select class="{{modifier_class}}" id="selectMultiItem" multiple>
<option>Option 1</option>
<option>Option 2</option>
<option>Option 3</option>
<optgroup label="More options">
<option>Option 4</option>
<option>Option 5</option>
</optgroup>
</select>
</div>
<div>
<label for="selectDisabled">A disabled drop-down</label>
<select class="{{modifier_class}}" id="selectDisabled" disabled>
<option>Option 1</option>
<option>Option 2</option>
<option>Option 3</option>
<optgroup label="More options">
<option>Option 4</option>
<option>Option 5</option>
</optgroup>
</select>
</div>
Source:
sass/base/forms/_forms.scss, line 255