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Mastering JavaScript classList: An Essential Skill for Web Developers

Introduction to JavaScript classList property

When crafting web pages and applications, we often need to apply various CSS styles to our elements to make them visually appealing. We can define these styles as classes and then use JavaScript to manipulate them.

The classList property is a useful feature in JavaScript that allows us to access and modify classes on an element. In this article, we will explore the classList property, its benefits, and how to manipulate classes using its various methods.

Representation of classList as a DOMTokenList object

The classList property is a read-only property that is represented as a DOMTokenList object. This object contains a list of classes assigned to an element, which can be manipulated using various methods.

The DOMTokenList object has several properties, including length, which returns the number of items in the list, and value, which returns a string representing all the classes in the list. Ability to manipulate classes using classList’s methods

One of the benefits of using classList is its built-in methods, which allow us to manipulate classes with ease.

The classList methods include add, remove, toggle, replace, item, and contains. 1.

add: This method allows us to add one or more classes to an element. We can pass one or multiple class names to this method, and it will add them to the element’s class attribute.

Example:

“`

element.classList.add(‘class1’, ‘class2’);

“`

2. remove: This method allows us to remove one or more classes from an element.

We can pass one or multiple class names to this method, and it will remove them from the element’s class attribute. Example:

“`

element.classList.remove(‘class1’, ‘class2’);

“`

3.

toggle: This method allows us to toggle a class on or off an element. If the class exists on the element, it will be removed, and if it doesn’t exist, it will be added.

Example:

“`

element.classList.toggle(‘class1’);

“`

4. replace: This method allows us to replace an existing class with a new one.

We can pass the old class name and the new class name to this method, and it will replace the old class with the new one. Example:

“`

element.classList.replace(‘old-class’, ‘new-class’);

“`

5.

item: This method allows us to retrieve a class name from the list based on its index. Example:

“`

var className = element.classList.item(0);

“`

6.

contains: This method allows us to check if an element has a specified class. It returns a boolean value indicating whether the class exists on the element.

Example:

“`

var hasClass = element.classList.contains(‘class1’);

“`

JavaScript classList examples

Now let’s take a look at some practical examples of using classList to manipulate classes on an element.

Getting CSS classes of an element

“`

var element = document.querySelector(‘.my-element’);

var classes = element.classList;

console.log(classes.value);

“`

In this example, we retrieve the classes of an element and log them to the console.

Adding one or more classes to an element

“`

var element = document.querySelector(‘.my-element’);

element.classList.add(‘new-class’);

“`

In this example, we add a new class named `new-class` to an element.

Removing one or more classes from an element

“`

var element = document.querySelector(‘.my-element’);

element.classList.remove(‘old-class’);

“`

In this example, we remove an old class named `old-class` from an element.

Replacing an existing class with a new one

“`

var element = document.querySelector(‘.my-element’);

element.classList.replace(‘old-class’, ‘new-class’);

“`

In this example, we replace an old class named `old-class` with a new class named `new-class` on an element.

Checking if an element has a specified class

“`

var element = document.querySelector(‘.my-element’);

var hasClass = element.classList.contains(‘selected’);

“`

In this example, we check if an element has a specified class named `selected`.

Toggling a class for an element

“`

var element = document.querySelector(‘.my-element’);

element.classList.toggle(‘selected’);

“`

In this example, we toggle a class named `selected` on or off an element.

Conclusion

The classList property is a useful feature in JavaScript that allows us to manipulate classes on an element with ease. Its built-in methods make it easy to add, remove, toggle, replace, check, and retrieve CSS classes from an element.

Understanding and utilizing the classList property can help improve the efficiency of our web development projects. JavaScript classList property is an essential and powerful tool available for modern-day web development.

The classList property returns a live collection of an element’s CSS classes and is represented as a DOMTokenList object. This live collection provides a direct path for web developers to make necessary changes to the CSS classes assigned to an element.

When combined with the methods provided by the classList object, developers can efficiently add, remove, replace, check, and toggle classes on web pages.

Returns Live Collection of CSS Classes

The primary function of the classList property is to return a live collection of an element’s CSS classes. This collection is unlike a standard string document returned by ‘className’, which cannot be manipulated easily.

Instead, classList provides a dynamic list of CSS classes assigned to an element, which can be interacted with using different inbuilt methods. To retrieve an element’s CSS classes using classList, we can utilize the following code:

“`

const element = document.getElementById(‘id’);

const classes = element.classList;

“`

As shown above, after capturing the element object with a specific ID or class, we can obtain its CSS classes by retrieving the classList object from it.

Once a collection of classes gets captured in the classList object, it becomes easy to interact with them using methods provided by the classList object. Methods for Adding, Removing, Replacing, Checking, and Toggling Classes

The live collection of CSS classes becomes beneficial to web developers when combined with the methods provided by classList.

The classList object grants access to several inbuilt methods that we can use to manipulate CSS classes. The following subsections will discuss several critical methods and how we can use them to modify CSS classes on web pages.

Method 1: add()

The add() method of the classList object allows developers to add one or multiple CSS classes to the collection of an element dynamically. We can pass one or multiple CSS classes separated by a comma to this method, and classList appends them to the element’s collection of CSS classes.

Here is an example script that illustrates the use of the add() method:

“`

const element = document.getElementById(‘id’);

element.classList.add(‘class1’, ‘class2’, ‘class3’);

“`

In the code above, we call the add() method while passing multiple classes. The code will append the CSS classes ‘class1’, ‘class2’, and ‘class3’ to the live collection of CSS classes for the HTML element with the specified ID.

Method 2: remove()

The remove() method helps developers remove CSS classes from an element. We can pass one or multiple CSS classes separated by a comma to this method.

The classList object then removes these CSS classes from the live collection of CSS classes for the target element. The script below demonstrates the usage of the remove() method:

“`

const element = document.getElementById(‘id’);

element.classList.remove(‘class1’, ‘class2’);

“`

In the example above, we remove the CSS classes ‘class1’ and ‘class2’ from the live collection of CSS classes for the HTML element with the specified ID.

Method 3: replace()

The replace() method of classList allows developers to substitute one CSS class with another at runtime. We can pass two parameters to the replace() method: the old CSS class, which we want to replace, and the new CSS class, which will replace it in the live collection of CSS classes for the target element.

Let’s look at an example of using the replace() method:

“`

const element = document.getElementById(‘id’);

element.classList.replace(‘old-class’, ‘new-class’);

“`

In the script above, we replace the old ‘old-class’ CSS class with the ‘new-class’ CSS class present in the live collection of CSS classes for the HTML element with the specified ID. Method 4: contains()

The contains() method of classList helps developers check whether a specified CSS class exists in the live collection of CSS classes on an element.

This method returns a boolean value of true or false based on the class’s presence. Here is an example script that demonstrates the usage of the contains() method:

“`

const element = document.getElementById(‘id’);

const classCheck = element.classList.contains(‘check-class’);

“`

In the script above, we check if the CSS class ‘check-class’ exists in the live collection of CSS classes for the HTML element with the specified ID.

Method 5: toggle()

The toggle() method of the classList object toggles a CSS class between its existence and non-existence in the live collection of CSS classes on an element. If the CSS class exists on the element, the method will remove it.

If the class is not there, it will add it. The script below demonstrates the use of toggle():

“`

const element = document.getElementById(‘id’);

element.classList.toggle(‘toggle-class’);

“`

In the above example, we toggle the CSS class ‘toggle-class’ on or off in the live collection of CSS classes for the specified element.

Conclusion

The classList property of JavaScript enables developers to access and interact with CSS classes of an element dynamically. It returns a live collection of CSS classes, which can be manipulated using built-in methods like add(), remove(), replace(), contains(), and toggle().

The combination of the classList property and its methods provides an efficient way for web developers to control the CSS classes of an element in real-time and can be an essential tool in web development. In conclusion, the classList property in JavaScript is a useful feature that enables developers to access and manipulate the CSS classes of an element dynamically.

It returns a live collection of CSS classes that can be interacted with using built-in methods such as add(), remove(), replace(), contains(), and toggle(). By utilizing classList, web developers can efficiently add or remove CSS classes based on user input, events, or other actions.

The combination of the classList property and its methods enhances front-end development, resulting in more responsive and interactive web pages. Overall, this article stresses the importance of using classList in web development and emphasizes that mastering it is a valuable takeaway for developers looking to improve their skills.

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