Intermediate JavaScript

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Advanced DOM Handling

The Document Object Model (DOM) is a programming interface that allows dynamic manipulation of a web page's elements. In this chapter, we will explore advanced techniques for working with the DOM efficiently and cleanly.

this image shows a DOM Diagram this image shows a DOM Diagram

Efficient Element Selection

The DOM offers several ways to select elements. It is essential to use efficient selectors, especially in applications with many elements.

javascript

"Here we use 'querySelector' to select an element with the ID 'submitButton' and 'querySelectorAll' to select all elements with the class 'list-item'."

Creation and Deletion of Elements

For manipulating the DOM, it is common to create and delete elements in real-time, especially in interactive applications.

javascript

"This code creates a new 'div' element with the text 'Hello World' and adds it to the end of the 'body'."

To remove an element, we can use the removeChild method or remove directly on the element.

javascript

"Here we select an element with the class 'item' and remove it using the 'remove' method."

Event Delegation

Event delegation is a technique that allows assigning a single event handler to a container instead of each individual element, improving performance.

javascript

"In this example, we add a click event to the container with the class 'list'. When an element with the class 'list-item' is clicked, the event is handled properly without needing to assign events to each individual element."

Advanced Style Manipulation

It is possible to change the styles of elements directly from JavaScript or manipulate classes to achieve more manageable style changes.

javascript

"In this code, we assign a blue background color directly to the element with the class 'box' and add the class 'active'."

Form Handling and Validation

JavaScript allows handling forms and performing validations in the DOM before sending data to the server.

javascript

"Here we prevent the form submission with 'event.preventDefault', and validate that the 'name' field is not empty."

Performance Optimization in DOM Manipulation

To improve performance, it is advisable to reduce the number of accesses and manipulations to the DOM.

Document Fragments

A DocumentFragment allows making changes to the DOM efficiently, applying multiple changes before inserting them into the document.

javascript

"In this example, we create a document fragment and add 'li' elements to it, before adding the entire fragment to the list in a single operation."

Intersection Observer

The IntersectionObserver allows observing elements when they enter or leave the view, which is useful for implementing effects like lazy loading or animations.

javascript

"Here we use 'IntersectionObserver' to observe images with the class 'lazy-image'. When an image enters the view, it is given the class 'visible'."

Conclusion

Advanced DOM handling in JavaScript allows building more dynamic and efficient user interfaces. By understanding how to select, create, and manipulate elements efficiently, you can improve the performance and usability of your applications.

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