recursion.js

recursion.js

let categories = [
  { id: 'animals', 'parent': null },
  { id: 'mammals', 'parent': 'animals' },
  { id: 'cats', 'parent': 'mammals' },
  { id: 'dogs', 'parent': 'mammals' },
  { id: 'chihuahua', 'parent': 'dogs' },
  { id: 'persian', 'parent': 'cats' },
  { id: 'siamese', 'parent': 'cats' },
]

function makeTree(categories, parent) {
  let node = {}

  categories
    .filter(x => x.parent === parent)
    .forEach(x => node[x.id] = makeTree(categories, x.id))

  return node
}

let tree = makeTree(categories, null)

console.log(
  JSON.stringify(tree, null, 2)
)


// outputs: 
// ##############################
// {
//   "animals": {
//     "mammals": {
//       "cats": {
//         "persian": {},
//         "siamese": {}
//       },
//       "dogs": {
//         "chihuahua": {}
//       }
//     }
//   }
// }