Find ancestors and Descendants in a Tree

tree.js

'use strict';

const findJob = (jobs, id) => {
  const found = jobs.filter(job => job.id === id);
  return found.length === 0 ? null : found[0];
};

const ancestors = (jobs, id, curr) => {
  if (!curr) {
    curr = [];
  }
  const job = findJob(jobs, id);
  if (job === null) {
    return curr;
  }
  if (!job.parent) {
    return curr;
  }
  return ancestors(jobs, job.parent, curr.concat([job.parent]));
};

// Verifica se candidateId é ancestral de descendantId
const isAncestor = (jobs, descendantId, candidateId) => (
  ancestors(jobs, descendantId).filter(ancestorId => ancestorId === candidateId).length > 0
);

// Verifica se candidateId é descendente de ancestorId
const isDescendant = (jobs, ancestorId, candidateId) => isAncestor(jobs, candidateId, ancestorId);

/*
     +-- 11 ----- 111
     |
 1 --+
     |
     +-- 12
     |
     |        +--- 14
     |        |
     +-- 13 --+
              |
              +--- 15

 2
*/
const jobs = [ {id: 15, parent: 13}, {id: 14, parent: 13}, {id: 13, parent: 1}, {id: 1, parent: null}, {id: 2, parent: null}, {id:11, parent: 1}, {id: 12, parent: 1}, {id: 111, parent: 11}];

// console.log(ancestors(jobs, 111));
// console.log(isAncestor(jobs, 111, 11));
// console.log(isAncestor(jobs, 111, 12));

// console.log(isDescendant(jobs, 1, 11));
// console.log(isDescendant(jobs, 11, 11));
// console.log(isDescendant(jobs, 1, 111));
// console.log(isDescendant(jobs, 11, 111));
// console.log(isDescendant(jobs, 2, 111));

// const descendants = (jobs, ancestorId) => jobs.map(job => job.id).reduce((result, elem) => {
//   if (isDescendant(jobs, ancestorId, elem)) {
//     result.push(elem);
//   }
//   return result;
// }, []);

// Sem o reduce, mas fazendo a mesma coisa
const descendants = (jobs, ancestorId) => {
  const result = [];
  jobs.map(job => job.id).forEach((elem) => {
    if (isDescendant(jobs, ancestorId, elem)) {
      result.push(elem);
    }
  });
  return result;
};

console.log(descendants(jobs, 1));
console.log(descendants(jobs, 13));