CSS Class

What is a Class Attribute?

A class attribute is a variable that belongs to a class as a whole, rather than to any specific instance of the class. It is defined within the class definition and is shared by all instances of the class. Class attributes are accessed using the class name itself and are common to all objects of that class. These attributes store data relevant to the entire class and define behaviors consistent across all instances of a class. Unlike instance attributes, changes to a class attribute are reflected in all instances of the class.

How is a Class Attribute Applied in HTML Elements?

In HTML the class attribute is used to assign a style or behavior to multiple elements sharing the same class. To apply a class to an HTML element you must first define the class in a CSS file or within the style section of an HTML document using the format;.classname. After defining it include the class attribute, in the opening tag of an HTML element.

Why Use Classes in CSS?

Utilizing classes in CSS boosts the aesthetics and manageability of a website.

1. Reusability; Defining and applying a class to elements helps in avoiding repetitive code and reducing the overall CSS file size.
2. Manageability; By assigning classes to elements making global design changes becomes more convenient. Modifying a class automatically updates all associated elements.
3. Organization; Classes categorize elements based on their purpose or design enhancing the readability and maintenance of the CSS code.
4. Separation of Concerns; CSS classes facilitate a distinction between presentation (CSS) and structure (HTML) on a website ensuring improved code organization and smoother collaboration, among developers.

Creating and Using Classes in CSS

Using classes in web design is a way to keep things organized and consistent. By assigning classes to elements on a website you can prevent repeating code and maintain a cohesive design, throughout various pages or sections.

Defining a Class in CSS

To define a CSS class, create a selector using the period symbol (.) followed by the class name. For example:

cssCopy code‍


.highlight {
    color: yellow;
    font-weight: bold;
}

Applying a Class to an Element

To apply a class to an element, add the class attribute to the opening tag of the element:

<p class="highlight">This is a paragraph.</p>


You can group classes together on one element by placing them next to each other with a space like this —

<div class="class1 class2">...</div>

To target elements with multiple classes, use multiple class selectors separated by a dot:

.class1.class2 {
    background-color: blue;
}

Overriding Styles with Classes

When you want to change the styles make a CSS class that has more influence, than the current one. You can do this by adding selectors or using the !important rule.

.existing-class {
    color: red;
}

.new-class {
    color: blue !important;
}

CSS Class Selectors

Understanding the .class Selector

The .class selector enables developers to add styles to elements with a particular class attribute assigned to them. For instance —

.my-class {
    font-size: 16px;
    color: green;
}

Specificity of Class Selectors

The specificity of class selectors is lower compared to ID selectors. If conflicting styles are applied to an element with both a class and an ID, the styles defined by the ID will take precedence.

Importance of Naming Conventions for Classes

Proper naming conventions in CSS classes contribute to code readability and maintainability. Commonly used conventions include camelCase for CSS definitions and kebab-case for HTML class attributes:

• CSS: .navigationBar
• HTML: class="navigation-bar"

Styling Elements with Classes

Applying Style Rules Using Classes

To apply style rules using classes:

1. Identify the elements that require the same styling.
2. Create a class in CSS.
3. Define the style rules for the class.
4. Apply the class to the elements in the HTML.

Example:

.my-class {
    color: red;
    font-size: 16px;
}

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


Using Shorthand Properties with Classes

When you use shorthand properties along with classes, in CSS you can set CSS properties in just one declaration. This makes your code more efficient. Helps cut down on repetition. For instance —

.my-class {
    margin: 10px 20px 30px 40px;
}

Utilizing shorthand properties alongside classes enhances the efficiency of web development ensures a consistent visual appeal, throughout your website.