An id on a <sub> tag assigns an identifier to the element.
The identifier must be unique across the page.
An id attribute on a <sub> tag.
The formula for water is H2O.
<p>
The formula for water is H<sub id="subtwo">2</sub>O.
</p>
The id attribute assigns an identifier to the <sub> element.
The id allows JavaScript to easily access the <sub> 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.
<sub 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 (.). |
A <sub> element with a unique id attribute.
Clicking the button displays the subscript content.
The formula for water is H2O
<p>The formula for water is H<sub id="mysub">2</sub>O</p>
<br />
<button onclick="show();">Show sub content</button>
<script>
let show = () => {
let element = document.getElementById("mysub");
alert("Content = " + element.innerHTML);
}
</script>
The id attribute assigns a unique identifier for the <sub>.
Clicking the button calls JavaScript which locates the <sub> using the id.
Finally, the content of the <sub> is displayed 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 <sub>
