HTML class Attribute
The HTML class attribute is used to specify a class for an HTML element. The class is used to group similar elements, to apply the same CSS design, or JavaScript code.
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 (CSS Code). It can also be used by a JavaScript to access and manipulate elements with the specific class name.
Style Sheet : The Style Sheet is the CSS Styles for Elements, specified with Class Name, ID, or Tag 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>
London
London is the capital of England.
Paris
Paris is the capital of France.
Tokyo
Tokyo is the capital of Japan.
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>
My Important Heading
This is some important text.
Tip: The class attribute can be used on any HTML element.
Note: The class name is case sensitive!
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>
London
London is the capital of England.
Paris
Paris is the capital of France.
Tokyo
Tokyo is the capital of Japan.
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
<!DOCTYPE html>
<html>
<head>
<style>
.city {
background-color: tomato;
color: white;
padding: 10px;
}
.main {
font-size: 25px;
}
</style>
</head>
<body>
<h2 class="city main">London</h2>
<h2 class="city">Paris</h2>
<h2 class="city">Tokyo</h2>
</body>
</html>
London
Paris
Tokyo
Different Elements Can Share Same Class
Different HTML elements can point to the same class name.
In the following example, both <h2> and <p> points 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>
Paris
Paris is the capital of France
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[i].style.display = "none";
}
}
</script>
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
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