symbol-tree

What is symbol-tree?

The symbol-tree package is a utility library for managing an ordered tree structure with symbols, allowing you to efficiently traverse and manipulate the tree without polluting the objects that make up the nodes of the tree. It is particularly useful when you need to maintain a tree of objects in memory and perform various operations on it without exposing the tree metadata on the objects themselves.

What are symbol-tree's main functionalities?

Creating and managing a tree structure

This feature allows you to create a tree and manage its structure by appending children to parent nodes. The tree structure is maintained internally using symbols.

{"const SymbolTree = require('symbol-tree');\nconst tree = new SymbolTree();\nconst parent = {};\nconst child1 = {};\nconst child2 = {};\ntree.appendChild(parent, child1);\ntree.appendChild(parent, child2);\nconsole.log(tree.firstChild(parent) === child1); // true\nconsole.log(tree.lastChild(parent) === child2); // true"}

Traversing the tree

This feature provides methods to traverse the tree, such as iterating over the children of a node. It allows for efficient tree traversal without exposing the internal structure.

{"const SymbolTree = require('symbol-tree');\nconst tree = new SymbolTree();\nconst parent = {};\nconst child = {};\ntree.appendChild(parent, child);\nfor(const node of tree.childrenIterator(parent)) {\n  console.log(node); // logs the `child` object\n}"}

Manipulating the tree

This feature includes methods to manipulate the tree, such as inserting nodes before or after a given node, which allows for dynamic changes to the tree structure.

{"const SymbolTree = require('symbol-tree');\nconst tree = new SymbolTree();\nconst parent = {};\nconst child = {};\nconst newParent = {};\ntree.appendChild(parent, child);\ntree.insertAfter(child, newParent);\nconsole.log(tree.nextSibling(child) === newParent); // true"}

Other packages similar to symbol-tree

domutils

The domutils package provides utilities for working with DOM trees. It offers functions for traversing, manipulating, and serializing DOM nodes. Compared to symbol-tree, domutils is specifically tailored for DOM operations and not for generic tree structures.

treenode

The treenode package is designed for creating and manipulating tree structures. It provides a TreeNode class with methods for adding children, searching, and traversing the tree. Unlike symbol-tree, treenode exposes the tree structure on the TreeNode instances themselves.

arborist

Arborist is a package that manages dependency trees in npm projects. While it deals with tree structures, its focus is on package dependency resolution and not on providing a generic tree manipulation API like symbol-tree.

README

symbol-tree

Turn any collection of objects into its own efficient tree or linked list using Symbol.

This library has been designed to provide an efficient backing data structure for DOM trees. You can also use this library as an efficient linked list. Any meta data is stored on your objects directly, which ensures any kind of insertion or deletion is performed in constant time. Because an ES6 Symbol is used, the meta data does not interfere with your object in any way.

Node.js 4+, io.js and modern browsers are supported.

Example

A linked list:

const SymbolTree = require('symbol-tree');
const tree = new SymbolTree();

let a = {foo: 'bar'}; // or `new Whatever()`
let b = {foo: 'baz'};
let c = {foo: 'qux'};

tree.insertBefore(b, a); // insert a before b
tree.insertAfter(b, c); // insert c after b

console.log(tree.nextSibling(a) === b);
console.log(tree.nextSibling(b) === c);
console.log(tree.previousSibling(c) === b);

tree.remove(b);
console.log(tree.nextSibling(a) === c);

A tree:

const SymbolTree = require('symbol-tree');
const tree = new SymbolTree();

let parent = {};
let a = {};
let b = {};
let c = {};

tree.prependChild(parent, a); // insert a as the first child
tree.appendChild(parent,c ); // insert c as the last child
tree.insertAfter(a, b); // insert b after a, it now has the same parent as a

console.log(tree.firstChild(parent) === a);
console.log(tree.nextSibling(tree.firstChild(parent)) === b);
console.log(tree.lastChild(parent) === c);

let grandparent = {};
tree.prependChild(grandparent, parent);
console.log(tree.firstChild(tree.firstChild(grandparent)) === a);

See api.md for more documentation.

Testing

Make sure you install the dependencies first:

npm install

You can now run the unit tests by executing:

npm test

The line and branch coverage should be 100%.

API Documentation

symbol-tree

Author: Joris van der Wel [e-mail]

• symbol-tree
  • SymbolTree ⏏
    • new SymbolTree([description])
    • .initialize(object) ⇒ Object
    • .hasChildren(object) ⇒ Boolean
    • .firstChild(object) ⇒ Object
    • .lastChild(object) ⇒ Object
    • .previousSibling(object) ⇒ Object
    • .nextSibling(object) ⇒ Object
    • .parent(object) ⇒ Object
    • .lastInclusiveDescendant(object) ⇒ Object
    • .preceding(object, [options]) ⇒ Object
    • .following(object, [options]) ⇒ Object
    • .childrenToArray(parent, [options]) ⇒ Array.<Object>
    • .ancestorsToArray(object, [options]) ⇒ Array.<Object>
    • .treeToArray(root, [options]) ⇒ Array.<Object>
    • .childrenIterator(parent, [options]) ⇒ Object
    • .previousSiblingsIterator(object) ⇒ Object
    • .nextSiblingsIterator(object) ⇒ Object
    • .ancestorsIterator(object) ⇒ Object
    • .treeIterator(root, options) ⇒ Object
    • .index(child) ⇒ Number
    • .childrenCount(parent) ⇒ Number
    • .compareTreePosition(left, right) ⇒ Number
    • .remove(removeObject) ⇒ Object
    • .insertBefore(referenceObject, newObject) ⇒ Object
    • .insertAfter(referenceObject, newObject) ⇒ Object
    • .prependChild(referenceObject, newObject) ⇒ Object
    • .appendChild(referenceObject, newObject) ⇒ Object

SymbolTree ⏏

Kind: Exported class

new SymbolTree([description])

Param	Type	Default	Description
[description]	string	"'SymbolTree data'"	Description used for the Symbol

symbolTree.initialize(object) ⇒ Object

You can use this function to (optionally) initialize an object right after its creation, to take advantage of V8's fast properties. Also useful if you would like to freeze your object.

O(1)

Kind: instance method of SymbolTree
Returns: Object - object

Param	Type
object	Object

symbolTree.hasChildren(object) ⇒ Boolean

Returns true if the object has any children. Otherwise it returns false.

• O(1)

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.firstChild(object) ⇒ Object

Returns the first child of the given object.

• O(1)

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.lastChild(object) ⇒ Object

Returns the last child of the given object.

• O(1)

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.previousSibling(object) ⇒ Object

Returns the previous sibling of the given object.

• O(1)

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.nextSibling(object) ⇒ Object

Returns the next sibling of the given object.

• O(1)

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.parent(object) ⇒ Object

Return the parent of the given object.

• O(1)

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.lastInclusiveDescendant(object) ⇒ Object

Find the inclusive descendant that is last in tree order of the given object.

• O(n) (worst case) where n is the depth of the subtree of object

Kind: instance method of SymbolTree

Param	Type
object	Object

symbolTree.preceding(object, [options]) ⇒ Object

Find the preceding object (A) of the given object (B). An object A is preceding an object B if A and B are in the same tree and A comes before B in tree order.

• O(n) (worst case)
• O(1) (amortized when walking the entire tree)

Kind: instance method of SymbolTree

Param	Type	Description
object	Object
[options]	Object
[options.root]	Object	If set, root must be an inclusive ancestor of the return value (or else null is returned). This check assumes that root is also an inclusive ancestor of the given object

symbolTree.following(object, [options]) ⇒ Object

Find the following object (A) of the given object (B). An object A is following an object B if A and B are in the same tree and A comes after B in tree order.

• O(n) (worst case) where n is the amount of objects in the entire tree
• O(1) (amortized when walking the entire tree)

Kind: instance method of SymbolTree

Param	Type	Default	Description
object	Object
[options]	Object
[options.root]	Object		If set, root must be an inclusive ancestor of the return value (or else null is returned). This check assumes that root is also an inclusive ancestor of the given object
[options.skipChildren]	Boolean	false	If set, ignore the children of object

symbolTree.childrenToArray(parent, [options]) ⇒ Array.<Object>

Append all children of the given object to an array.

• O(n) where n is the amount of children of the given parent

Kind: instance method of SymbolTree

Param	Type	Default	Description
parent	Object
[options]	Object
[options.array]	Array.<Object>	[]
[options.filter]	function		Function to test each object before it is added to the array. Invoked with arguments (object). Should return true if an object is to be included.
[options.thisArg]	*		Value to use as this when executing filter.

symbolTree.ancestorsToArray(object, [options]) ⇒ Array.<Object>

Append all inclusive ancestors of the given object to an array.

• O(n) where n is the amount of ancestors of the given object

Kind: instance method of SymbolTree

Param	Type	Default	Description
object	Object
[options]	Object
[options.array]	Array.<Object>	[]
[options.filter]	function		Function to test each object before it is added to the array. Invoked with arguments (object). Should return true if an object is to be included.
[options.thisArg]	*		Value to use as this when executing filter.

symbolTree.treeToArray(root, [options]) ⇒ Array.<Object>

Append all descendants of the given object to an array (in tree order).

• O(n) where n is the amount of objects in the sub-tree of the given object

Kind: instance method of SymbolTree

Param	Type	Default	Description
root	Object
[options]	Object
[options.array]	Array.<Object>	[]
[options.filter]	function		Function to test each object before it is added to the array. Invoked with arguments (object). Should return true if an object is to be included.
[options.thisArg]	*		Value to use as this when executing filter.

symbolTree.childrenIterator(parent, [options]) ⇒ Object

Iterate over all children of the given object

• O(1) for a single iteration

Kind: instance method of SymbolTree
Returns: Object - An iterable iterator (ES6)

Param	Type	Default
parent	Object
[options]	Object
[options.reverse]	Boolean	false

symbolTree.previousSiblingsIterator(object) ⇒ Object

Iterate over all the previous siblings of the given object. (in reverse tree order)

• O(1) for a single iteration

Kind: instance method of SymbolTree
Returns: Object - An iterable iterator (ES6)

Param	Type
object	Object

symbolTree.nextSiblingsIterator(object) ⇒ Object

Iterate over all the next siblings of the given object. (in tree order)

• O(1) for a single iteration

Kind: instance method of SymbolTree
Returns: Object - An iterable iterator (ES6)

Param	Type
object	Object

symbolTree.ancestorsIterator(object) ⇒ Object

Iterate over all inclusive ancestors of the given object

• O(1) for a single iteration

Kind: instance method of SymbolTree
Returns: Object - An iterable iterator (ES6)

Param	Type
object	Object

symbolTree.treeIterator(root, options) ⇒ Object

Iterate over all descendants of the given object (in tree order).

Where n is the amount of objects in the sub-tree of the given root:

• O(n) (worst case for a single iteration)
• O(n) (amortized, when completing the iterator)

Kind: instance method of SymbolTree
Returns: Object - An iterable iterator (ES6)

Param	Type	Default
root	Object
options	Object
[options.reverse]	Boolean	false

symbolTree.index(child) ⇒ Number

Find the index of the given object (the number of preceding siblings).

• O(n) where n is the amount of preceding siblings
• O(1) (amortized, if the tree is not modified)

Kind: instance method of SymbolTree
Returns: Number - The number of preceding siblings, or -1 if the object has no parent

Param	Type
child	Object

symbolTree.childrenCount(parent) ⇒ Number

Calculate the number of children.

• O(n) where n is the amount of children
• O(1) (amortized, if the tree is not modified)

Kind: instance method of SymbolTree

Param	Type
parent	Object

symbolTree.compareTreePosition(left, right) ⇒ Number

Compare the position of an object relative to another object. A bit set is returned:

• DISCONNECTED : 1
• PRECEDING : 2
• FOLLOWING : 4
• CONTAINS : 8
• CONTAINED_BY : 16

The semantics are the same as compareDocumentPosition in DOM, with the exception that DISCONNECTED never occurs with any other bit.

where n and m are the amount of ancestors of left and right; where o is the amount of children of the lowest common ancestor of left and right:

• O(n + m + o) (worst case)
• O(n + m) (amortized, if the tree is not modified)

Kind: instance method of SymbolTree

Param	Type
left	Object
right	Object

symbolTree.remove(removeObject) ⇒ Object

Remove the object from this tree. Has no effect if already removed.

• O(1)

Kind: instance method of SymbolTree
Returns: Object - removeObject

Param	Type
removeObject	Object

symbolTree.insertBefore(referenceObject, newObject) ⇒ Object

Insert the given object before the reference object. newObject is now the previous sibling of referenceObject.

• O(1)

Kind: instance method of SymbolTree
Returns: Object - newObject
Throws:

• Error If the newObject is already present in this SymbolTree

Param	Type
referenceObject	Object
newObject	Object

symbolTree.insertAfter(referenceObject, newObject) ⇒ Object

Insert the given object after the reference object. newObject is now the next sibling of referenceObject.

• O(1)

Kind: instance method of SymbolTree
Returns: Object - newObject
Throws:

• Error If the newObject is already present in this SymbolTree

Param	Type
referenceObject	Object
newObject	Object

symbolTree.prependChild(referenceObject, newObject) ⇒ Object

Insert the given object as the first child of the given reference object. newObject is now the first child of referenceObject.

• O(1)

Kind: instance method of SymbolTree
Returns: Object - newObject
Throws:

• Error If the newObject is already present in this SymbolTree

Param	Type
referenceObject	Object
newObject	Object

symbolTree.appendChild(referenceObject, newObject) ⇒ Object

Insert the given object as the last child of the given reference object. newObject is now the last child of referenceObject.

• O(1)

Kind: instance method of SymbolTree
Returns: Object - newObject
Throws:

• Error If the newObject is already present in this SymbolTree

Param	Type
referenceObject	Object
newObject	Object