The class attribute assigns one or more classnames to the <optgroup> tag.
Classnames are defined in a stylesheet or in a local <style> element.
Classes, i.e. classnames, are used to style elements.
Two <optgroup> elements with class attributes.
<style>
.optgroup { font-size: 20px; }
.teal { color: teal; }
.tomato { color: tomato; }
</style>
<select>
<option value="">-- Select city -- </option>
<optgroup class="optgroup teal" label="Europe">
<option value="stockholm">Stockholm</option>
<option value="barcelona">Barcelona</option>
<option value="athens">Athens</option>
</optgroup>
<optgroup class="optgroup tomato" label="Asia">
<option value="bangkok">Bangkok</option>
<option value="manila">Manila</option>
<option value="jakarta">Jakarta</option>
</optgroup>
</select>
Classes (i.e. classnames) are used for styling the optgroup element.
Multiple classnames are separated by a space.
JavaScript uses classes to access elements by classname.
Tip: class is a global attribute that can be applied to any HTML element.
<optgroup class="classnames">
| Value | Description |
|---|---|
| classnames | One or more space-separated class names. |
A class attribute styles an <optgroup> element.
Clicking the button toggles a classname that changes the font size.
<style>
.optgroup-sm {font-size: 16px;color: teal;}
.optgroup-lg {font-size: 20px;}
</style>
<select>
<option value="">-- Select city -- </option>
<optgroup id="myoptgroup" class="optgroup-sm" label="Europe">
<option value="stockholm">Stockholm</option>
<option value="barcelona">Barcelona</option>
<option value="athens">Athens</option>
</optgroup>
</select>
<br />
<button onclick="toggle();">Toggle class</button>
<script>
let toggle = () => {
let element = document.getElementById("myoptgroup");
element.classList.toggle("optgroup-lg");
}
</script>
Two CSS classes are defined in the <style> element.
The class attribute in <optgroup> assigns a single classname.
Repeatedly clicking the button toggles the second class, resizing the <optgroup> font size.
Notice how the <options> inside changes its font size as well.
Here is when class support started for each browser:
 Chrome
|
1.0 | Sep 2008 |
 Firefox
|
1.0 | Sep 2002 |
 IE/Edge
|
1.0 | Aug 1995 |
 Opera
|
1.0 | Jan 2006 |
 Safari
|
1.0 | Jan 2003 |
Back to <optgroup>
