Finding a path to target object in nested array of objects in Javascript

Question

I'm currently working through a problem that I'm having some trouble figuring out where I need to find a child node in an array of objects. The target could be one or many levels deep.

The issue is, once I find the object, I also need to push the path I took to get to that object into the resulting data array.

Currently, I have written code that can successfully find the child node:

const buildFullTree = (tree, cat, data = []) => {
  let collection = [tree]

  while (collection.length) {
    let node = collection.shift()

    if (node.id === cat.id) {
      data.push(node)
    }

    collection.unshift(...node.children)
  }

  return data
}

However, this isn't sufficient in terms of getting the path taken to that object.

I'm pretty sure that I need to change this to a recursive depth-first search solution in order to achieve what I'm looking for, but I am not sure how to change the while loop to accomplish this.

Answer 1

If I understand your question correctly, then perhaps you could revise your path search function like so to achieve what you require:

 const buildFullTree = (departmentTree, category, data = []) => { const findPath = (node, category) => { //If current node matches search node, return tail of path result if (node.id === category.id) { return [node] } else { //If current node not search node match, examine children. For first //child that returns an array (path), prepend current node to that //path result for (const child of node.children) { const childPath = findPath(child, category) if (Array.isArray(childPath)) { childPath.unshift(child) return childPath } } } } const foundPath = findPath(departmentTree, category) // If search from root returns a path, prepend root node to path in // data result if (Array.isArray(foundPath)) { data.push(departmentTree) data.push(...foundPath) } return data } const departmentTree = { id: 5, title: 'department', level: 1, children: [{ id: 1, parentId: 5, title: 'category', level: 2, children: [{ id: 15, parentId: 1, title: 'subcategory', level: 3, children: [] }, { id: 18, parentId: 1, level: 3, title: 'subcategory', children: [] }, { id: 26, parentId: 1, level: 3, title: 'subcategory', children: [{ id: 75, parentId: 26, level: 4, title: 'sub-subcategory', children: [] }, { id: 78, parentId: 26, level: 4, title: 'sub-subcategory', children: [] }] }] }, { id: 23823, title: 'category', level: 2, children: [] }, { id: 9, parentId: 5, level: 2, title: 'category', children: [{ id: 48414, parentId: 9, level: 3, title: 'subcategory', children: [] }, { id: 2414, parentId: 9, level: 3, title: 'subcategory', children: [] }, { id: 42414, parentId: 9, level: 3, title: 'subcategory', children: [{ id: 2323213, parentId: 42414, level: 4, title: 'sub-subcategory', children: [] }, { id: 322332, parentId: 42414, level: 4, title: 'sub-subcategory', children: [] }] }] }] }; console.log('Path to 2323213:', buildFullTree(departmentTree, { id: 2323213 }).map(node => node.id).join(' -> ')) console.log('Path to 23823:', buildFullTree(departmentTree, { id: 23823 }).map(node => node.id).join(' -> ')) console.log('Path to -1 (non existing node):', buildFullTree(departmentTree, { id: -1 }).map(node => node.id).join(' -> '))