easy-tree

easy-tree

This simple Node.js module provides an easy way to manipulate tree data structures.

Usage

Require the module and create a Tree object:

var Tree = require('easy-tree');

// Create an empty tree
var tree = new Tree();

// Create a tree from an arbitrary data object
var tree = new Tree({
    a : 1,
    b : 2
});

// Create a tree with several children from an array
var tree = new Tree([
    { a : 1 },
    { b : 2 }
]);

// Create a multi-level tree using the `children` property
var tree = new Tree({
    a : 1,
    b : 2,
    children : [
        { c : 3 },
        { d : 4 }
    ]
});

// If you're not a fan of `new`
var tree = Tree();

A Tree object represents a tree node. Tree nodes must be JavaScript objects. They can have any data attributes that do not conflict with Tree object method names, and one or more children, which are stored in the children array.

You can use tree.children[i] and tree.children.length to retrieve and count children, but do not manipulate the children array directly! Instead, use the following methods to safely and correctly perform operations on the tree:

Methods

Most methods take a path argument which is an array of 0-based indices that point to a tree node. Omit the path argument or use [] to perform the operation on the current node, but this is not valid for all operations: a tree node cannot remove itself, or insert a node before or after itself, because it doesn't know its own parent.

Many methods take a child argument, which can be either a Tree instance or a plain object which will be converted to a Tree instance.

tree.get([path])

Returns the subtree at path (or the tree itself, if path is [] or omitted).

tree.prepend([path], child)

Insert child as the first child of the node given by path.

Returns the new number of children of the modified node.

tree.insertBefore(path, child)

Insert child before the node given by path.

path cannot be omitted and must contain at least 1 element.

Returns the new number of children of the modified node.

tree.append([path], child)

Insert child as the last child of the node given by path.

Returns the new number of children of the modified node.

tree.insertAfter(path, child)

Insert child after the node given by path.

path cannot be omitted and must contain at least 1 element.

Returns the new number of children of the modified node.

tree.remove(path)

Removes the node specified by path, and inserts each of its children where the removed node used to be.

path cannot be omitted and must contain at least 1 element.

Returns the removed node (without any children).

tree.prune(path)

Removes the entire subtree beginning with the node specified by path.

path cannot be omitted and must contain at least 1 element.

Returns the removed node and all its children.

tree.keys([path])

Returns an array of all data attributes in the node specified by path (same as Object.keys() but excludes the children property).

tree.walk([path], [cb])

For the node specified by path and any child and descendant nodes, calls cb synchronously with parameters path, node.

Returns the total number of nodes visited.

You can omit the cb parameter to just count the number of nodes in a tree.

If cb returns false for a given node, the walk function will not descend to that node's children and they will not be included in the count of nodes visited.

Other Notes

Tree objects also contain the following private methods, so you cannot use any of these names as data attributes:

• _doAtPath
• _makeTree
• _throwPathError
• _walk

Saving tree data to JSON and restoring it later works just fine:

var myTree = new Tree({ ... });

var savedData = JSON.stringify(myTree);

myTree = new Tree(JSON.parse(savedData));