The DOM and JavaScript
We'll dive deeper into the DOM by discussing DOM data types and the properties and methods used to access DOM elements using JavaScript.
Read this article and locate the methods used with the "window" and "document" objects. For example, when a program uses an alert, it uses the "window.alert" method. JavaScript uses the "window.onload" method when a page is loaded. When a user clicks an element on a page, the "onclick" method is called. Remember that calling a method for an object uses dot (.) notation.
The Document Object Model (DOM) is a programming interface for web documents. It represents the page so that programs can change the document structure, style, and content. The DOM represents the document as nodes and objects; that way, programming languages can interact with the page.
A web page is a document that can be either displayed in the browser window or as the HTML source. In both cases, it is the same document but the Document Object Model (DOM) representation allows it to be manipulated. As an object-oriented representation of the web page, it can be modified with a scripting language such as JavaScript.
For example, the DOM specifies that the querySelectorAll method in this code snippet must return a list of all the <p> elements
in the document:
const paragraphs = document.querySelectorAll("p"); // paragraphs[0] is the first <p> element // paragraphs[1] is the second <p> element, etc. alert(paragraphs[0].nodeName);
All of the properties, methods, and events available for manipulating and creating web pages are organized into objects. For example, the document object that represents the document itself, any table objects
that implement the HTMLTableElement DOM interface for accessing HTML tables, and so forth, are all objects.
The DOM is built using multiple APIs that work together. The core DOM defines the entities describing any document and the objects within it. This is expanded upon as needed by other APIs that add new features and capabilities to the DOM. For example, the HTML DOM API adds support for representing HTML documents to the core DOM, and the SVG API adds support for representing SVG documents.