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Chapter 17. The Document Object Model > Using the Core DOM API

17.2. Using the Core DOM API

Now that we've studied the tree structure of documents and seen how the tree is composed of Node objects, we can move on to study the Node object and document trees in more detail. As I noted previously, the core DOM API is not terribly complex. The following sections contain examples that demonstrate how you can use it to accomplish common tasks.

17.2.1. Traversing a Document

As we've already discussed, the DOM represents an HTML document as a tree of Node objects. With any tree structure, one of the most common things to do is traverse the tree, examining each node of the tree in turn. Example 17-1 shows one way to do this. It is a JavaScript function that recursively examines a node and all its children, adding up the number of HTML tags (i.e., Element nodes) it encounters in the course of the traversal. Note the use of the childNodes property of a node. The value of this property is a NodeList object, which behaves (in JavaScript) like an array of Node objects. Thus, the function can enumerate all the children of a given node by looping through the elements of the childNodes[] array. By recursing, the function enumerates not just all children of a given node, but all nodes in the tree of nodes. Note that this function also demonstrates the use of the nodeType property to determine the type of each node.


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