JavaScript: The Definitive Guide, Fourth Edition

DOM Compatibility with Internet Explorer 4

Although IE 4 is not DOM-compliant, it has features that are similar to the core DOM APIs. These features are not part of the DOM standard and are not compatible with Netscape, but they are compatible with later versions of IE. The features are summarized here; consult the client-side reference section of this book for more details.

Traversing a Document

The DOM standard specifies that all Node objects, which includes both the Document object and all Element objects, have a childNodes[] array that contains the children of that node. IE 4 does not support childNodes[], but it provides a very similar children[] array on its Document and HTMLElement objects. Thus, it is easy to write a recursive function like the one shown in Example 17-1 to traverse the complete set of HTML elements within an IE 4 document.

There is one substantial difference between IE 4’s children[] array and the standard DOM childNodes[] array, however. IE 4 does not have a Text node type and does not consider strings of text to be children. Thus, a <p> tag that contains only plain text with no markup has an empty children[] array in IE 4. As we’ll see shortly, however, the textual content of a <p> tag is available through the IE 4 innerText property.

Finding Document Elements

IE 4 does not support the getElementById( ) and getElementsByTagName( ) methods of the Document object. Instead, the Document object and all document elements have an array property named all[] ...