An id on an <optgroup> tag assigns an identifier to the element.
The identifier must be unique across the page.
An id attribute on 2 <optgroup> tags.
<select>
<option value="">-- Select city -- </option>
<optgroup id="european-cities" label="Europe">
<option value="stockholm">Stockholm</option>
<option value="barcelona">Barcelona</option>
<option value="athens">Athens</option>
</optgroup>
<optgroup id="asian-cities" label="Asia">
<option value="bangkok">Bangkok</option>
<option value="manila">Manila</option>
<option value="jakarta">Jakarta</option>
</optgroup>
</select>
The id attribute assigns an identifier to the <optgroup> element.
The id allows JavaScript to easily access the <optgroup> element.
It is also used to point to a specific id selector in a style sheet.
Tip: id is a global attribute that can be applied to any HTML element.
<optgroup id="identifier" />
| Value | Description |
|---|---|
| identifier | A unique alphanumeric string. The id value must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens (-), underscores (_), colons (:), and periods (.). |
An <optgroup> tag with a unique id.
Clicking the button displays the number of <option> elements inside the option group.
<select>
<option value="">-- Select city -- </option>
<optgroup id="myoptgroup" label="Europe">
<option value="stockholm">Stockholm</option>
<option value="barcelona">Barcelona</option>
<option value="athens">Athens</option>
</optgroup>
</select>
<br/>
<button onclick="show();">Show # options</button>
<script>
let show = () => {
let element = document.getElementById("myoptgroup");
let itemCount = element.getElementsByTagName("option").length;
alert("Option count = " + itemCount);
}
</script>
The id attribute assigns a unique identifier for the <optgroup>.
Clicking the button calls JavaScript which locates the <optgroup> through the id.
Then counts the number of <option> tag inside the <optgroup> and displays it in an alert box.
Here is when id 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>
