HTML <sub> class Attribute

The class attribute on a <sub> tag assigns one or more classnames to the subtext element. Classes are used to style elements. Classnames are defined in a stylesheet or in a local <style> element.

Example

#

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>

Using class

The class attribute assigns one or more classnames to the <sub> tag.

Multiple classnames are separated by a space.

Classes (i.e. classnames) are used for styling the sub element.

JavaScript uses classes to access one or more elements by classname.

Tip:  class is a global attribute that can be applied to any HTML element.


Syntax

<sub class="classnames">

Values

#

Value Description
classnames One or more space-separated class names.

More Examples

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>

Code explanation

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.


Browser support

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

You may also like

 Back to <sub>
Guides