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An HTML tree is a way of displaying information as nested nodes that can be expanded or collapsed. It is used to organize and display information, such as in online bulletin boards, and requires the use of dynamic HTML (DHTML) to allow nodes to be expanded or collapsed.
A computer data tree is a method of displaying information as a sequence of nested nodes that can be expanded or collapsed to show subheadings or other information. In HyperText Markup Language (HTML), a tree implementation is often known as a tree view. An HTML tree can be used to show the layout of pages within a given website; the titles and subtitles of a draft, document, or book; or the topics and answers in a forum. There is no single way to implement an HTML tree, and HTML itself has no built-in support for a tree view. Instead, an HTML tree is usually constructed using a combination of tools which collectively are referred to as dynamic HTML (DHTML).
An HTML tree is used when there is a collection of information that can be viewed linearly, and each top-level entry might have zero or more information that can be related to that entry. Each entry is called a node and can have other nodes nested under it. An example of an instance where a tree could be used to organize and display information is within an online bulletin board.
Each topic in an online bulletin board might be listed as a top-level node, with the term “top level” indicating that the node is not nested under another node. Each response to a single topic is nested under the top-level node or parent topic. If an answer is answered, the first answer becomes a node under which the second is nested. In this way, information can be organized so that top-down associations can be represented visually, usually by increasing the indentation of each line in relation to how deeply it is nested in the structure.
One aspect of an HTML tree that requires the use of DHTML is the ability for each node to be expanded, showing all nodes below it, or collapsed, hiding all nodes so that only the top-level node is seen. This can be achieved through the use of an HTML table that is manipulated via a scripting language that modifies the Document Object Model (DOM) to show or hide the necessary table cells. Another method used to create a dynamic HTML tree is to use extensible markup language (XML) documents that are transformed into HTML pages with server-side script or other modules.
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