15.1. Interfaces

The HTML Document Object Model is an application programming interface (API) that defines the structure of an HTML document in the browser. In addition, it defines how that document can be accessed and manipulated through the use of JavaScript, sometimes embedded within the very same HTML document that is being manipulated.

This sounds a little scary doesn't it? The idea that a JavaScript routine could essentially modify the very fabric of its own universe can be terrifying. Just one oops, and it is overit modified itself right out of existence. For all intents and purposes, as far as the browser was concerned, it would have never existed. Fortunately, this takes a little work to accomplish, and only the JavaScript function and possibly the associated page would cease to exist. Believe me, if this wasn't the case, I would have winked out long ago.

Table 15-1 shows the various HTML Document Object Model interfaces available through JavaScript. I would like to point out that the majority of these interfaces correspond to actual HTML elements. Yes, name an HTML element, and there is a corresponding interface; remember, though, that just because an interface exists for a deprecated element, you don't have to use it. It is still deprecated.

Table 15-1. HTML Document Object Model Interfaces Available Through JavaScript

Interface Name	Description
HTMLCollection	A collection of HTML nodes
HTMLDocument	The root element of the HTML document
HTMLElement	The base class for all HTML elements
HTMLHtmlElement	Corresponds to the html element
HTMLHeadElement	Corresponds to the head element
HTMLLinkElement	Corresponds to the link element
HTMLTitleElement	Corresponds to the title element
HTMLMetaElement	Corresponds to the meta element
HTMLBaseElement	Corresponds to the base element
HTMLIsIndexElement	Corresponds to the isindex element
HTMLStyleElement	Corresponds to the style element
HTMLBodyElement	Corresponds to the body element
HTMLFormElement	Corresponds to the form element
HTMLSelectElement	Corresponds to the select element.
HTMLOptGroupElement	Corresponds to the option group element
HTMLOptionElement	Corresponds to the option element
HTMLInputElement	Corresponds to the input element
HTMLTextAreaElement	Corresponds to the text area element
HTMLButtonElement	Corresponds to the button element
HTMLLabelElement	Corresponds to the label element
HTMLFieldSetElement	Corresponds to the field set element
HTMLLegendElement	Corresponds to the legend element
HTMLUListElement	Corresponds to the unordered list element
HTMLOListElement	Corresponds to the ordered list element
HTMLDListElement	Corresponds to the dash list element
HTMLDirectoryElement	Corresponds to the directory element
HTMLMenuElement	Corresponds to the menu element
HTMLLIElement	Corresponds to the list element
HTMLBlockquoteElement	Corresponds to the block quote element
HTMLDivElement	Corresponds to the div element
HTMLParagraphElement	Corresponds to the paragraph element
HTMLHeadingElement	Corresponds to the heading elements
HTMLQuoteElement	Corresponds to the quote element
HTMLPreElement	Corresponds to the preformatted element
HTMLBRElement	Corresponds to the break element
HTMLBaseFontElement	Corresponds to the base font element
HTMLFontElement	Corresponds to the font element
HTMLHRElement	Corresponds to the horizontal rule element
HTMLModElement	Corresponds to the modification elements
HTMLAnchorElement	Corresponds to the anchor element
HTMLImageElement	Corresponds to the image element
HTMLObjectElement	Corresponds to the object element
HTMLParamElement	Corresponds to the parameter element
HTMLAppletElement	Corresponds to the applet element
HTMLMapElement	Corresponds to the map element
HTMLAreaElement	Corresponds to the area element
HTMLScriptElement	Corresponds to the script element
HTMLTableElement	Corresponds to the table element
HTMLTableCaptionElement	Corresponds to the table caption element
HTMLTableColElement	Corresponds to the table column element
HTMLTableSectionElement	Corresponds to the table section element
HTMLTableRowElement	Corresponds to the table row element
HTMLTableCellElement	Corresponds to the table cell element
HTMLFrameSetElement	Corresponds to the frame set element
HTMLFrameElement	Corresponds to the frame element
HTMLIFrameElement	Corresponds to the iframe element

15.1.1. Window

Although it's not officially part of the HTML Document Object Model, the window object is the big kahuna, the big cheese, or, in web development terms, top of the hierarchy. Many web developers don't realize it, but all HTML documents are actually children of the window object. This means that it is as valid to code window.document as it is to code document. You will probably see only the latter as opposed to the former, but I think it's a good idea to point out the possibility of the former, if only to avoid those Homer Simpson moments: Doh!