What is DOM | Document Object Model | Beginner Tutorial

Summary

In this session, Raghav introduces the Document Object Model (DOM), explaining its core concept of representing XML and HTML documents as tree structures. He covers how DOM enables developers to easily read, access, and update the content of web pages. Through practical examples, such as using DOM viewers and JavaScript, Raghav demonstrates how to manipulate elements like title and author in XML documents. He also highlights how browsers use DOM for rendering and allows dynamic interaction through developer tools. The session concludes with a discussion on DOM’s role in web automation tools like Selenium.

Takeaways

• 😀 DOM (Document Object Model) represents HTML and XML documents as a tree structure.
• 😀 The root element of an XML document is represented at the top of the DOM tree, with child elements branching out underneath.
• 😀 DOM allows developers to access, read, and modify content in a structured way using programming languages like JavaScript.
• 😀 XML can be visualized as a tree structure, where each tag and element is a node in the tree.
• 😀 The DOM API enables interaction with document elements using methods like `getElementsByTagName`.
• 😀 DOM is used to modify content on web pages through scripts, enabling dynamic changes in HTML or XML documents.
• 😀 The DOM tree is created in memory by browsers, allowing real-time access and modification through JavaScript.
• 😀 Browser developer tools provide a built-in DOM viewer to inspect and manipulate elements on a webpage.
• 😀 DOM is a core concept in web automation, with tools like Selenium using DOM to interact with web elements during automated testing.
• 😀 Using DOM, web pages can be dynamically altered, as shown in a demo where a title in an XML document was modified programmatically.
• 😀 DOM is not limited to static documents; it plays a central role in creating interactive, dynamic web experiences.

Q & A

What is the Document Object Model (DOM)?

The Document Object Model (DOM) is a programming interface that represents the content of XML or HTML documents as a tree structure. It allows developers to interact with and manipulate the document's elements using programming languages, most commonly JavaScript.

How does DOM represent an XML or HTML document?

DOM represents an XML or HTML document as a hierarchical tree structure. The root element is at the top, with child elements branching underneath it, creating a parent-child relationship between the elements.

Can DOM be used with programming languages other than JavaScript?

Yes, DOM is a programming interface that can be used with various programming languages. Although it's most commonly used with JavaScript, it can also be used with other languages such as Python, Java, and C++.

What is the significance of the 'getElementsByTagName' function in DOM?

The 'getElementsByTagName' function is used in DOM to retrieve all elements with a specific tag name from a document. This function allows developers to easily access and manipulate elements based on their tag name.

How does the tree structure in DOM relate to an XML document?

In an XML document, the structure of elements is converted into a tree in DOM, where the root element (e.g., <Books>) is at the top, and child elements (e.g., <book>, <author>, <price>) form branches under it. This tree structure is then used to access and modify the document's content.

What is the purpose of DOM in web browsers?

In web browsers, DOM serves as a representation of the HTML document, allowing for dynamic interactions and modifications of the webpage's elements using JavaScript. DOM is crucial for tasks such as form handling, content updates, and element manipulation in web development.

How can DOM be used in web automation tools like Selenium?

In web automation tools like Selenium, DOM is used to identify and interact with elements on a webpage. Tools like XPath use the DOM structure to locate elements, allowing automated tests to perform actions such as clicking buttons, filling forms, and validating content.

What is an example of DOM manipulation in the browser's inspect tool?

In the browser's inspect tool, you can modify a webpage's content by directly interacting with its DOM. For example, if you right-click on a 'login' button and inspect it, you can change the button's text value from 'login' to 'start' in the DOM, which will immediately reflect on the page.

What are some common DOM functions besides 'getElementsByTagName'?

Other common DOM functions include 'getElementById' (to access an element by its ID), 'getElementsByClassName' (to access elements by class name), 'querySelector' (to select elements using CSS selectors), and 'createElement' (to create new elements in the document).

What is the role of DOM in modifying the content of a webpage?

DOM allows developers to dynamically modify the content of a webpage by accessing elements and updating their properties. This could involve changing text, styles, or attributes, or adding/removing elements, all through JavaScript or other programming languages.