What is the DOM?

• DOM stands for Document Object Model
• can be a bit tricky to wrap your head around. It is essentially a set of objects and methods that defines how your HTML document is accessed and manipulated.
• A central metaphor of the DOM is that your HTML file is a tree, and HTML elements are branches and leaves on that tree.
• A visual representation of the DOM can be seen by using the 'Inspect' feature of your browser.

Please try this out right now, on this web page!

Is the DOM Just My HTML?

• No, it isn't. :-)
• The DOM can appear similar or identical to the HTML that makes up your website. However, browsers can fix small syntax errors in your HTML automatically (such as inserting a missing close tag).
• The DOM is also kept up to date with the current state of the page, even if it is modified using JavaScript.
• JavaScript isn't actually editing your document. It is simply modifying the DOM. You can think of the DOM as an editable copy of your read-only website, which stays pristine on your server or filesystem.

Unbreaking Your Code (Using the DOM)

With both HTML and CSS, it can be easy to forget a semi-colon or a closing tag, which can lead to unwanted display issues on your website. There are a few tools that can help prevent and/or fix this going forward.

• Your Browser
• A Friend
• A Linter

Debugging With Your Browser

Chrome can be one of the most useful tools for debugging HTML and CSS.

• Right clicking on an element in Chrome. You will see an option labeled 'Inspect'.
• An easy-to-read visual representation of your DOM will open, which can be modified and analyzed to track down any code that may be of issue.
• Both CSS properties and HTML elements can also be added, removed, or modified to determine their impact on specific elements of your web page.

Grab a Second Set of Eyes

Often staring at thousands of semi-colons and angle brackets can be overwhelming and mind-numbing. A second set of trained eyes can help to find that pesky character that is breaking your code.

What is a Linter?

• A program that assesses code in order to locate any possible errors

There are endless options for both HTML and CSS linters. A quick Google search will yield a number of potential websites and plugins to help debug your code.

E.g. https://validator.w3.org/