HTML: ID & Class

In HTML, id and class are attributes used to add identifiers and apply styles to elements. While they serve similar purposes, they have distinct differences in their usage:

id Attribute:

• The id attribute is used to uniquely identify an element on a web page. Each id value must be unique within the entire HTML document.
• You can use the id attribute to target specific elements with CSS or JavaScript.
• Example:

<div id="header">This is the header</div>
<p id="content">This is the main content</p>

class Attribute:

• The class attribute is used to apply one or more class names to an element. Multiple elements can share the same class name.
• Classes are typically used to apply CSS styles to multiple elements that share common styling characteristics.
• Example:

<p class="highlighted">This text is highlighted</p>
<p class="highlighted">So is this one</p>

Usage Differences:

id Usage:

• Used to uniquely identify an element.
• Each id value must be unique within the HTML document.
• Typically used for elements that appear only once on the page or have unique functionality.
• Example usage in CSS: #header { color: blue; }
• Example usage in JavaScript: document.getElementById('header')

class Usage:

• Used to apply common styling or behavior to multiple elements.
• Multiple elements can share the same class name.
• Classes allow for easier and more efficient styling across multiple elements.
• Example usage in CSS: .highlighted { background-color: yellow; }
• Example usage in JavaScript (for multiple elements): document.querySelectorAll('.highlighted')

Best Practices:

• Use id when you need to uniquely identify an element, such as a specific section or component on the page.
• Use class when multiple elements share the same styling or functionality.
• Avoid using the same ID for multiple elements as it violates HTML standards and can lead to unexpected behavior in CSS and JavaScript.

Here's a summary of the differences:

• id: Uniquely identifies an element, that must be unique within the document.
• class: Applies one or more class names to elements, and allows for shared styling across multiple elements.

By understanding the differences between id and class, you can use them effectively to structure your HTML and apply styles and functionality to your web pages.