< JavaScript Programming

This lesson introduces the JavaScript Document Object Model (DOM) and Browser Object Model (BOM).

Objectives and Skills

Objectives and skills for this lesson include:[1]

  • Identify and construct the Document Object Model (DOM) tree
    • window; document; body; other HTML elements
  • Complete and debug code that outputs to an HTML document
    • innerHTML; document.write
  • Complete and debug code that interacts with the Browser Object Model (BOM)
    • Manage state; display dialogs; determine screen size


  1. Wikipedia: Document Object Model
  2. Wikipedia: Browser Object Model
  3. Wikibooks: JavaScript/Introduction to the Document Object Model (DOM)


  1. YouTube: JavaScript Tutorial for Beginners - 25 - Document Object Model
  2. YouTube: JavaScript Tutorial for Beginners - 40 - Traversing the DOM
  3. YouTube: JavaScript Tutorial for Beginners - 41 - Traversing the DOM Part 2
  4. YouTube: JavaScript Tutorial for Beginners - 42 - Traversing the DOM Part 3
  5. YouTube: JavaScript Tutorial for Beginners - 52 - Window object
  6. YouTube: An Introduction to the DOM (Document Object Model) in JavaScript
  7. YouTube: Document Object Model Tutorial
  8. Youtube: Javascript DOM Manipulation



Complete the following activities using external JavaScript code. Apply JavaScript best practices, including comments, indentations, naming conventions, and constants. Use input elements for input and respond to input or change events, add buttons and respond to click events, or set a timer interval and respond to interval events. Use HTML elements for output. Use separate functions for each type of processing. Avoid global variables by passing parameters and returning results. Create test data to validate the accuracy of each program. Add comments at the top of the program and include references to any resources used.

  1. Create JavaScript code to display all tags in the current HTML document using document.getElementByTagName("*").
  2. Create JavaScript code to display the nodeName and nodeType for all nodes in the current HTML document using childNodes. Use a JavaScript object (key/value pairs) to look up the nodeType and convert the type number to a string description.
  3. Create JavaScript code to display the current window size, screen size, and location information. Use the resize event to update the display whenever the window size changes.

Lesson Summary

  • The Document Object Model (DOM) defines a standard for accessing documents.[2]
  • The Browser Object Model (BOM) allows JavaScript to "talk to" the browser.[3]
  • In the HTML DOM, the Element object represents an HTML element, like P, DIV, A, TABLE, or any other HTML element.[4]
  • Parent-child relationships within the DOM can be used to target document elements. It is possible to move (traverse) from parent to child (downwards), from child to parent (upwards), and from sibling to sibling (sideways).[5]
  • HTML DOM is a standard for how to get, change, add, or delete HTML elements.[6]

Key Terms

Browser Object Model (BOM)
The API of the browser that allows JavaScript to communicate with the browser.[7]
Document Object Model (DOM)
The data representation of the objects that comprise the structure and content of a document on the web.[8]
An HTML element. The "DOM" is a tree structure that represents the HTML of the website, and every HTML element is a "node". More specifically, "Node" is an interface that is implemented by multiple objects.

See Also


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