tree-visit

A tree traversal library.

npm install --save tree-visit

OR

yarn add tree-visit

API

The recommended way to use tree-visit is by calling defineTree(getChildren), where getChildren is a function which returns a node's children as an array. The defineTree API returns an object containing every library function with the getChildren option already set.

You may alternately import individual functions, e.g. visit, and pass the { getChildren } option when calling them. Importing individual functions can reduce your bundle size to the bear minimum (though the entire library is small and has 0 dependencies, so this may not be necessary).

Most callback functions, such as getChildren, predicate, onEnter, and onLeave, are passed an IndexPath as the second argument, containing an array of integer indexes that identify that node. The root node is implicitly included in the IndexPath (i.e. there's no 0 first in every IndexPath).

• access
• accessPath
• defineTree
• diagram
• find
• findAll
• findIndexPath
• flat
• visit

access

Returns a node by its IndexPath.

Type: function access<T>(node: T, indexPath: IndexPath, options: BaseOptions<T>): T

Example

import { access } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

access(rootNode, [1, 0], { getChildren })
// #=> { name: 'd' }

accessPath

Returns an array of each node in an IndexPath.

Type: function accessPath<T>(node: T, indexPath: IndexPath, options: BaseOptions<T>): T

Example

import { accessPath } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

access(rootNode, [1, 0], { getChildren })
// #=> [{ name: 'a', children: [...] }, { name: 'c', children: [...] }, { name: 'd' }]

defineTree

Returns a version of every library function with the getChildren option already set.

This also allows for more concise calls to most functions.

Type: function defineTree<T>(baseOptions: BaseOptions<T>): Tree<T>

Example

import { defineTree } from 'tree-visit'

const getChildren = (node) => node.children || []

const { visit, find } = defineTree({ getChildren })

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

visit(rootNode, (node) => {
  console.log(node)
})
// #=> a, b, c, d

find(rootNode, (node) => node.name === 'd')
// #=> { name: 'd' }

diagram

Generate a diagram of the tree, as a string.

Type: function diagram<T>(node: T, options: DiagramOptions<T>): string

Example

import { diagram } from 'tree-visit'

const getChildren = (node) => node.children || []
const getLabel = (node) => node.name

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

diagram(rootNode, { getChildren, getLabel })
// #=> a
// #=> ├── b
// #=> └── c / d

find

Find a node matching a predicate function.

Type: function find<T>(node: T, options: FindOptions<T>): T | undefined

Example

import { find } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

find(rootNode, { getChildren, predicate: (node) => node.name === 'd' })
// #=> { name: 'd' }

findAll

Find all nodes matching a predicate function.

Type: findAll<T>(node: T, options: FindOptions<T>): T[]

Example

import { findAll } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

findAll(rootNode, { getChildren, predicate: (node) => node.name === 'd' })
// #=> [{ name: 'd' }]

findIndexPath

Find the IndexPath of a node matching a predicate function.

Type: findIndexPath<T>(node: T, options: FindOptions<T>): T[]

Example

import { findIndexPath } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

findIndexPath(rootNode, { getChildren, predicate: (node) => node.name === 'd' })
// #=> [1, 0]

findAllIndexPaths

Find the IndexPath of all nodes matching a predicate function.

Type: findAllIndexPaths<T>(node: T, options: FindOptions<T>): T[]

Example

import { findAllIndexPaths } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

findAllIndexPaths(rootNode, {
  getChildren,
  predicate: (node) => node.name === 'c' || node.name === 'd',
})
// #=> [[1], [1, 0]]

flat

Returns an array containing the root node and all of its descendants.

This is analogous to Array.prototype.flat for flattening arrays.

Type: function flat<T>(node: T, options: BaseOptions<T>): T[]

Example

import { flat } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

flat(rootNode, { getChildren }).map((node) => node.name)
// #=> ['a', 'b', 'c', 'd']

visit

Visit each node in the tree, calling an optional onEnter and onLeave for each.

From onEnter:

• return nothing or undefined to continue
• return "skip" to skip the children of that node and the subsequent onLeave
• return "stop" to end traversal

From onLeave:

• return nothing or undefined to continue
• return "stop" to end traversal

Type: function visit<T>(node: T, options: VisitOptions<T>): void

Example

import { visit } from 'tree-visit'

const getChildren = (node) => node.children || []

const rootNode = {
  name: 'a',
  children: [
    { name: 'b' },
    {
      name: 'c',
      children: [{ name: 'd' }],
    },
  ],
}

visit(rootNode, {
  getChildren,
  onEnter: (node) => {
    console.log(node)
  },
})
// #=> a, b, c, d