HTML Class and Id Attributes

HTML provides two attributes, class and id, that allow developers to add custom attributes to elements in order to identify or style them.

The Id Attribute

The id attribute is used to give an element a unique identifier. The value of the id attribute must be unique within the HTML document, and it can be used to target a specific element with CSS or JavaScript. The syntax for the id attribute is as follows:

1<element id="unique_id">

Here's an example of using the id attribute to target a specific element:

1<p id="my-paragraph">This is a paragraph.</p>

You can use the # symbol in CSS to target the element with the given id. Here's an example of applying a red color to the paragraph above:

1#my-paragraph {
2  color: red;
3}

The Class Attribute

The class attribute is used to group elements that have similar characteristics. Multiple elements can have the same class attribute value. The syntax for the class attribute is as follows:

1<element class="class_name">

Here's an example of using the class attribute to group multiple elements:

1<p class="my-class">This is a paragraph.</p>
2<div class="my-class">This is a div.</div>

You can use the . symbol in CSS to target elements with the given class. Here's an example of applying a red color to all elements with the my-class class:

1.my-class {
2  color: red;
3}

Difference Between Class and Id

The main difference between the class and id attributes is that the id attribute is used to uniquely identify an element, while the class attribute is used to group elements that have similar characteristics. An id must be unique within the HTML document, while multiple elements can have the same class.

Here are some other differences between class and id:

• You can use the class attribute to target multiple elements with CSS, while the id attribute is used to target a single element.
• In JavaScript, you can use the getElementById method to get the element with the given id. There is no equivalent method for getting elements by class name.
• The class attribute is more commonly used than the id attribute, as it is often more useful to group elements with similar characteristics rather than targeting a specific element.