Section 2.5. Static W3C HTML DOM Objects
2.5. Static W3C HTML DOM ObjectsOne category of DOM object not explicitly detailed in this chapter is the one containing the static DOM objects from which each HTML element object instance is derived. By and large you won't ever have need to script these static objects directly, although you will see their names crop up in your debugging in browsers such as Mozilla and recent versions of Safari and Opera. For example, if you ask the alert( ) method to display the reference to a p element object in Mozilla, the reference is converted to a string form as follows: [object HTMLParagraphElement] This is not the object's JavaScript type (which is just object). But it means that the p element in question is an instance of the W3C DOM HTMLParagraphElement object. In browsers that support direct access to the static object (Mozilla, Safari after version 2.0.4, and Opera 8 or later), you have the luxury of adding properties and methods to the prototype property of any such object. Thus, any new instance that your scripts create has those new properties and methods built into them (see the Array.prototype description in Chapter 5 for an example of this JavaScript mechanism). The W3C DOM Level 2 module for HTML elements defines the static objects in the following list. All of these objects inherit the properties and methods of the HTMLElement object, also listed below. Descriptions for these items can be found later in this chapter under the HTML element object names (e.g., HTMLParagraphElement is covered under the p object).
When a browser implements an element that is not part of the HTML 4 and W3C DOM specification, it typically extends the HTMLDivElement or HTMLSpanElement object with behaviors and/or styles to give that elements it's special characteristics. Thus, Mozilla reports that a marquee element is derived from the HTMLSpanElement object. |
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