treezy

🌲 treezy is a tiny and fast Node.js package for creating and manipulating hierarchal (tree-shaped) data.

Installation

In Node.js (version 16+), install with npm:

npm install treezy

Example usage

A tree can be any JavaScript object that contains an array of children, where each child is another JavaScript object that matches the structure of its parent.

For example, here's a tree with three nodes 👇

//   A
//  / \
// B   C

const myTree = {
  id: "A",
  children: [
    { id: "B", children: [] },
    { id: "C", children: [] }
  ],
}

treezy makes it easy to do things like...

Count the number of nodes in the tree

import { getSize } from "treezy"

getSize(myTree) 
// Returns: 3

Check if the tree contains at least one node with id equal to "Q"

import { contains } from "treezy"

contains(myTree, { testFn: (x) => x.id === "Q" }) 
// Returns: false

Extract the subtree starting at the node with id equal to "B"

import { getSubtree } from "treezy"

getSubtree(myTree, { testFn: (x) => x.id === "B" }) 
// Returns: { id: "B", children: [] }

Notes

• By default, treezy functions never modify their inputs by reference
• treezy expects every node in a tree to include an array with child nodes
• treezy always scans in depth-first search, pre-order
• treezy expects every tree to have exactly one root node (at depth 0)
• The parent of a root node is null

API

• apply(tree, options) - apply some function to nodes in a tree
• bifurcate(tree, options) - split a tree into two subtrees
• contains(tree, options) - check if a tree contains a node that passes some test
• getDepth(tree, options?) - get the number of nodes in a tree
• getParent(tree, options) - get the parent node of some other node
• getSignature(tree, options) - combine the node ids and structure into a unique id
• getSize(tree, options?) - count the number of nodes in a tree
• getSubtree(tree, options) - retrieve the subtree of a tree starting at some node
• getValues(tree, options?) - retrieve the nodes or node properties as an array
• insert(tree, options) - insert one tree into another
• prune(tree, options) - delete nodes matching some criteria
• reduce(tree, options) - apply a reducer function to a tree

All functions come with an options parameter that let you specify things such as

• copy: should the input tree be copied prior to modification?
• childrenProp: name of the array property in the tree storing child nodes
• testFn: a function applied to each node, to test whether it matches some criteria

See each function's type definitions for its comprehensive documentation.

Examples

Suppose you have data for a comment thread on a YouTube video..

const comment = {
  id: 234424,
  userId: 489294,
  text: "I like dogs",
  likes: 2,
  replies: [
    {
      id: 248210,
      userId: 403928,
      text: "So do I!",
      likes: 1,
      replies: [],
    },
    {
      id: 211104,
      userId: 407718,
      text: "Meh, cats are better",
      likes: 0,
      replies: [
        {
          id: 248210,
          userId: 489294,
          text: "Kick rocks, dummy head",
          likes: 3,
          replies: [],
        },
      ],
    }
  ],
}

How do I count the total number of comments?

import { getSize } from "treezy"

getSize(comment) // 4

How do I count the number of comments by a particular user?

import { getSize } from "treezy"

getSize(comment, { testFn: (node) => node.userId === 489294 }) // 2

How do I determine the max number of likes given to any single comment?

import { reduce } from "treezy"

const reducer = (node, initVal) => Math.max(node.likes, initVal)
reduce(comment, { reduceFn: reducer, initialVal: 0 }) // 3

How do I flatten the comments into a 1-D array?

import { getValues } from "treezy"

getValues(comment) // [{id: 234424, ...}, {id: 248210, ...}, ...]

How do I retrieve all the comment values?

import { getValues } from "treezy"

getValues(comment, { getFn: (node) => node.text })
// ["I like dogs", "So do I!", ...]

How do I remove comments which are replies to replies, or deeper?

import { prune } from "treezy"

prune(comment, { testFn: (node, parent, depth) => depth >= 2 })