The class attribute assigns one or more classnames to the <sub> tag.
Classnames are defined in a stylesheet or in a local <style> element.
Classes, i.e. classnames, are used to style elements.
A class attribute styling a <sub> element.
The formula for water is H2O
<style>
.red { color:red;font-weight:bold; }
</style>
<p>The formula for water is H<sub class="red">2</sub>O</p>
Classes (i.e. classnames) are used for styling the sub 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.
<sub class="classnames">
| Value | Description |
|---|---|
| classnames | One or more space-separated class names. |
A class attribute styling a <sub> element.
Clicking the button toggles a classname that boldens the subscript text.
The formula for water is H2O.
<style>
.teal { color: teal; }
.bold { font-weight:bold; }
</style>
<p>The formula for water is H<sub id="mysub" class="teal">2</sub>O.</p>
<br />
<button onclick="toggle();">Toggle class</button>
<script>
let toggle = () => {
let element = document.getElementById("mysub");
element.classList.toggle("bold");
}
</script>
Two CSS classes are defined in the <style> element.
The class attribute in <sub> assigns one classname.
Repeatedly clicking the button adds and removes another class, toggling the boldness of the element.
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 <sub>
