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What Is Shadow DOM? | DOM vs Shadow DOM

Intro

A common problem that cyber warriors face is encapsulation. One of the turtles that are the basis of object-oriented programming is the basis of modern software engineering. How do I create a boundary between the code I write and the code I use? Besides SVG, today’s web platforms only provide built-in mechanisms to separate one code from another, and that’s pretty ugly. Yes, I’m talking about iframes. The frame is too heavy and restrictive for most packing needs.

DOM

The basis of a web page consists of HTML, a markup language that humans must describe and understand. HTML provides a way to add structure and content, but the machine needs more methods. Therefore, the Document Object Model (aka DOM) was created. The DOM contains APIs that applications can use to manipulate a document’s structure, content, and style.

Shadow DOM

Shadow DOM is a secondary tree of DOM nodes. These Shadow DOM subtrees can associate with an element, but are not represented as children of the element. Instead, the subtree forms its scope. For example, a shadow DOM subtree might contain IDs and styles that overlap a document, but the shadow DOM subtree is separate from the document (unlike a list of child nodes), so the IDs and styles are ignored in the shadow DOM subtree. It does not match the content of the document.

Shadow DOM is no secret that you need to enable or install. It is created by the browser in a completely separate DOM tree called Shadow Tree. Shadow Tree comes with its elements and styles which are added as children to the element. The element that adds to the tree is called the Shadow host and the root is called the shadow DOM.

In a sense, shadow DOM is a “lightweight” version of DOM. Just like the DOM, it is a representation of an HTML element that determines the content to display on the page and allows the element to be modified. However, unlike the DOM, the shadow DOM is not based on a complete, self-contained document. As the name suggests, a shadow DOM is always associated with a normal DOM element. Without DOM, there is no shadow DOM.

Recommended to Read:- Handling Shadow Dom In Selenium 4

DOM vs Shadow DOM

In a sense, shadow DOM is a “lightweight” version of DOM. Just like the DOM, it is a representation of an HTML element that determines the content to display on the page and allows the element to be modified. However, unlike the DOM, the shadow DOM is not based on a complete, self-contained document. As the name suggests, a shadow DOM is always associated with a normal DOM element. Without DOM, there is no shadow DOM.

Shaded DOM Style

I can’t count the number of times I’ve had CSS scoping issues in my career. This is partly due to extended selectors such as divs, and excessive use of inappropriate CSS namespace. Additionally, replacing a widget’s CSS can be difficult, and the widget’s CSS can overflow and affect the application-level CSS. Avoiding these issues becomes more difficult as the application scales, especially if multiple developers are working with the code base. Proper standards can help mitigate these issues, but since most applications use open source libraries such as jQuery UI, Kendo UI, Bootstrap, etc., proper standards are not enough. Solving these issues and providing a standard way to apply styles to delimited elements are two benefits of using Shadow DOM.

How Does Shadow DOM Works?

To illustrate how Shadow DOM works, recreate Twitter’s “follow” button using Shadow DOM instead of <iframe>. We start first with the ghost host. This is a simple HTML element of the original DOM that adds a new shadow DOM. Components such as the follow button can also contain fallback elements that display if JavaScript is not enabled or ghost DOM is not supported on the page. It’s not just the <a> element that serves as a ghost host. This is because some elements (mainly interactive elements) cannot be shadow hosts.

To attach the DOM Shadow to the host, use the attack shadow() method. This will create an empty shadow root as a child of the shadow DOM. Just as the <html> element is the starting point of the original DOM, the shadow root is the starting point of the new shadow DOM. You can use #shadow-root to show the shadow path in the Devtools inspector.

Raw HTML children are visible to the inspector but are no longer visible on the page when the shadow DOM takes over. Then create the content that forms the new ghost tree. A ghost tree is similar to a DOM tree, but instead of a normal DOM, it’s a shadow DOM. To create a button, you need a new <a> element with an icon almost identical to the existing fallback link. Use the appendChild() method to add this new element to the Shadow DOM, just like adding any element as a child of another element. Finally, you can add multiple styles

Author BIO

Rahul Sakthi is working at Devstringx Technologies, a pioneer in Independent software testing companies globally. Rahul has 05 years of experience in manual & automation software testing. He is a technical expert, a passionate writer, and a seasoned IT professional. He enjoys connecting with people and keeping himself updated with the latest in the field of business, and technology.

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