When a browser loads a web page, it does not simply display the HTML file as text. It reads (parses) the markup and builds an in-memory model of the document: a structured collection of objects that represent every element, attribute, and piece of text on the page. That model is the Document Object Model, or DOM. Because it is made of objects, JavaScript can read it, search it, and change it while the page is running.
This topic is the conceptual foundation for the rest of the module and for much of the rest of the course. Before you can select elements, change styles, or add new content with code, you need a clear mental picture of what you are actually working with: a tree of nodes rooted at the document object, with parent, child, and sibling relationships that mirror the nesting of your HTML tags. You should also understand why the DOM exists at all — it is a standardized interface that lets a scripting language talk to a document that was written in a markup language.
As you watch the videos below, look for three things. First, the distinction between your HTML source file and the DOM the browser builds from it, since they are related but not identical. Second, the vocabulary of the tree: document, element nodes, text nodes, attributes, parent and child. Third, how JavaScript reaches into that tree through the document object. Try opening your browser's developer tools alongside the videos and inspect a simple page of your own so the abstract tree becomes something you can see.
Part of CodeWithHarry's Sigma Web Development course, this tutorial introduces the Document Object Model from a JavaScript developer's point of view. Based on its title and placement in a JavaScript series, it should explain what the DOM is, how the document object represents the loaded page, and how JavaScript uses it to reach the content of an HTML document. Expect live demonstration in the browser console rather than slides alone.
It frames the DOM specifically as the interface between HTML and JavaScript, which is the core idea of this topic, and it comes from a widely followed, beginner-friendly web development series that keeps the pace brisk and practical.
This beginner tutorial from Automation Step by Step walks through the definition of the Document Object Model, the reasons it is needed, and a short demonstration of using it. The description explicitly lists what the DOM is, why we need it, and how to use it, so it should cover both the concept and a first look at working with it in a browser.
It directly addresses the "defining the DOM" and "why the DOM exists" subtopics in plain language, making it a good first watch before moving on to tree structure and code details.
This video focuses narrowly on the DOM tree itself, using a live DOM tree viewer to show how the hierarchical structure of a page is built from HTML markup. It should help you see how nested tags become parent and child nodes and how text inside elements appears as its own node in the tree.
It gives a visual, concrete treatment of the "DOM as a tree structure" and "how browsers create the DOM" subtopics, which is exactly the mental model you need before learning selection and manipulation methods.
Together these videos support MO1 most directly: they define the DOM, explain why browsers construct it from HTML markup, and visualize the resulting hierarchy of document, element, and text nodes. By presenting the DOM as the interface through which JavaScript reaches page content, they also lay the groundwork for the selection, manipulation, and node-creation outcomes (MO3, MO4, MO5), since every selector and method you will use later operates on the tree described here. Script loading behavior (MO2) is covered elsewhere in the module, but understanding that the DOM is built progressively as the parser reads the document is the prerequisite idea these videos establish.
These videos were chosen from YouTube on October 3, 2026. Each has captions; the player turns them on. Videos on YouTube can be changed or removed — if one no longer plays, tell your instructor. If a player does not appear, use its Watch on YouTube link.