HTML class Attribute
The HTML class attribute is
used to specify a class for an HTML element.
Multiple HTML elements can share the same class.
Using The class Attribute
The class attribute is often used to point
to a class name in a style sheet. It can also be used by a JavaScript to access and
manipulate elements with the specific class name.
In the following example we have three <div> elements
with a class attribute with the value of
"city". All of the three <div>
elements will be styled equally according to the .city
style definition in the head section:
Example
<!DOCTYPE html><html><head><style>
.city { background-color: tomato; color: white;
border: 2px solid black; margin: 20px;
padding: 20px;} </style>
</head><body><div class="city">
<h2>London</h2> <p>London is the capital of England.</p>
</div><div class="city">
<h2>Paris</h2> <p>Paris is the capital of France.</p></div><div class="city">
<h2>Tokyo</h2> <p>Tokyo is the capital of Japan.</p></div></body></html>
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In the following example we have two <span> elements
with a class attribute with the value of
"note". Both <span>
elements will be styled equally according to the .note
style definition in the head section:
Example
<!DOCTYPE html><html><head><style>.note {
font-size: 120%; color: red;}
</style></head><body><h1>My <span class="note">Important</span> Heading</h1><p>This is some <span class="note">important</span> text.</p></body></html>
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Tip: The class attribute can be used on any HTML element.
Note: The class name is case sensitive!
Tip: You can learn much more about CSS in our CSS Tutorial.
The Syntax For Class
To create a class; write a period (.) character, followed by a
class name.
Then, define the CSS properties within curly braces {}:
Example
Create a class named "city":
<!DOCTYPE html><html><head><style>.city {
background-color: tomato; color: white; padding: 10px;
}</style></head><body><h2 class="city">London</h2>
<p>London is the capital of England.</p><h2 class="city">Paris</h2>
<p>Paris is the capital of France.</p><h2 class="city">Tokyo</h2>
<p>Tokyo is the capital of Japan.</p></body></html>
Try it Yourself »
Multiple Classes
HTML elements can belong to more than one class.
To define multiple classes, separate the class names with a space, e.g. <div
class="city main">. The element will be styled according to all the
classes specified.
In the following example, the first <h2> element belongs to both the
city class and also to the main class,
and will get the CSS styles from both of the classes:
Example
<h2
class="city main">London</h2><h2 class="city">Paris</h2><h2
class="city">Tokyo</h2>
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Different Elements Can Share Same Class
Different HTML elements can point to the same class name.
In the following example, both <h2> and <p>
point to the "city" class
and will share the same style:
Example
<h2 class="city">Paris</h2><p
class="city">Paris is the capital of France</p>
Try it Yourself »
Use of The class Attribute in JavaScript
The class name can also be used by JavaScript to perform certain tasks for
specific elements.
JavaScript can access elements with a specific class name with the getElementsByClassName() method:
Example
Click on a button to hide all elements with the class name
"city":
<script>function myFunction() { var x = document.getElementsByClassName("city"); for (var i = 0; i < x.length;
i++) { x.style.display = "none"; }}</script>
Try it Yourself »
Don't worry if you don't understand the code in the example above.
You will learn more about JavaScript in our HTML JavaScript chapter, or you can study our
JavaScript Tutorial.
Chapter Summary
The HTML class attribute specifies one or
more class names for an element
Classes are used by CSS and JavaScript to select and access specific
elements
The class attribute can be used on any
HTML element
The class name is case sensitive
Different HTML elements can point to the same class name
JavaScript can access elements with a specific class name with the getElementsByClassName()
method
HTML Exercises
Test Yourself With Exercises
Exercise:
Create a class selector named "special".
Add a color property with the value "blue" inside the "special" class.
<!DOCTYPE html>
<html>
<head>
<style>
;
</style>
</head>
<body>
<p class="special">My paragraph</p>
</body>
</html>
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Start the Exercise
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Reference: https://www.w3schools.com/html/html_classes.asp