How Can I Dynamically Manage Element Classes in JavaScript?

How Can I Dynamically Change an Element's Class with JavaScript?

Modern HTML5 Techniques for Class Manipulation

Modern browsers support the classList property, which provides convenient methods to add, remove, or toggle classes without needing external libraries:

document.getElementById("MyElement").classList.add('MyClass');
document.getElementById("MyElement").classList.remove('MyClass');
if ( document.getElementById("MyElement").classList.contains('MyClass') )
document.getElementById("MyElement").classList.toggle('MyClass');

Cross-Browser Solutions

Changing All Classes

To replace all existing classes with new ones, use className:

document.getElementById("MyElement").className = "MyClass";

Adding an Additional Class

Append a space and the new class name:

document.getElementById("MyElement").className += " MyClass";

Removing a Class

Use a regular expression replace:

document.getElementById("MyElement").className =
document.getElementById("MyElement").className.replace(/(?:^|\s)MyClass(?!\S)/g , '');

Checking if a Class is Applied

if ( document.getElementById("MyElement").className.match(/(?:^|\s)MyClass(?!\S)/) )

Event Handling

You can assign these actions to onclick or other events by:

• Calling a function in the onClick attribute:

<button onClick="changeClass()"></button>

• Using addEventListener in JavaScript:

document.getElementById("MyElement").addEventListener('click', changeClass);

JavaScript Frameworks and Libraries

Frameworks and libraries simplify these tasks, such as jQuery:

$('#MyElement').addClass('MyClass');
$('#MyElement').click(changeClass);

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