HTML DOM Node Tree
The HTML DOM views a HTML document as a node-tree.
All the nodes in a node tree have relationships to each other.
The HTML DOM Node Tree (Document Tree)
The HTML DOM views a HTML document as a tree-structure. The tree structure is
called a node-tree.
All nodes can be accessed through the tree. Their contents can be modified or
deleted, and new elements can be created.
The node tree below shows the set of nodes, and the connections between them.
The tree starts at the root node and branches out to the text nodes at the
lowest level of the tree:
Node Parents, Children, and Siblings
The nodes in the node tree have a hierarchical relationship to each other.
The terms parent, child, and sibling are used to describe the relationships.
Parent nodes have children. Children on the same level are called siblings
(brothers or sisters).
- In a node tree, the top node is called the root
- Every node, except the root, has exactly one parent node
- A node can have any number of children
- A leaf is a node with no children
- Siblings are nodes with the same parent
Look at the following HTML fragment:
<h1>DOM Lesson one</h1>
In the HTML above, every
node except for the document node has a parent node:
- The <html> node has no parent node; the root node
- The parent node of
the <head> and <body> nodes is the <html> node
- The parent node of the "Hello world!" text node is the <p> node
Most element nodes have child nodes:
- The <html> node has two child nodes; <head> and <body>
- The <head> node has one
child node; the <title> node
- The <title> node also has one child
node; the text node "DOM Tutorial"
- The <h1> and <p> nodes are siblings, and both child nodes of <body>
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