How Can I Efficiently Manipulate JavaScript Element Classes?

JavaScript Class Manipulation Techniques

Changing an Element's Class on Demand

To modify an element's class dynamically based on events like clicks, JavaScript offers several approaches:

Modern HTML5 Class Manipulation

Modern browsers support classList, which simplifies class handling:

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

For browsers that lack classList, use these methods:

Replace All Classes

Set the className attribute to replace all existing classes:

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

Add a Class

Append a space and the new class name to the existing className:

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

Remove a Class

Use a regex to remove a specific class without affecting others:

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

Check if a Class Exists

Use the same regex for class removal to check for a class's presence:

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

Attaching Functions to onClick Events

Wrap these actions in functions and call them from event handlers:

function changeClass() {
  // Code examples from above
}
document.getElementById("MyElement").addEventListener('click', changeClass);

JavaScript Frameworks and Libraries

Frameworks like jQuery streamline class manipulation:

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

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