JavaScript: The Definitive Guide, Fourth Edition

Name

NodeList — a read-only array of nodes

Availability

DOM Level 1 Core

Properties

readonly unsigned long length

The number of nodes in the array.

Methods

item( )

Returns the specified element of the array.

Description

The NodeList interface defines a read-only ordered list (i.e., an array) of Node objects. The length property specifies how many nodes are in the list, and the item( ) method allows you to obtain the node at a specified position in the list. The elements of a NodeList are always valid Node objects: NodeLists never contain null elements.

In JavaScript, NodeList objects behave like JavaScript arrays, and you can query an element from the list using square-bracket array notation instead of calling the item( ) method. However, you cannot assign new nodes to a NodeList using square brackets. Since it is always easier to think of a NodeList object as a read-only JavaScript array, this book uses the notation Node[] (i.e., a Node array) instead of NodeList. See Element.getElementsByTagName( ), for example, which is listed as returning a Node[] instead of a NodeList object. Similarly, the childNodes property of the Node object is technically a NodeList object, but the “Node” reference page defines it as a Node[], and the property itself is usually referred to as “the childNodes[] array.”

Note that NodeList objects are “live”: they are not static, but immediately reflect changes to the document tree. For example, if you have a NodeList that represents the children of a specific ...