Taking an array of objects and representing as a tree using recursion

recursion.js

// Basic Recursion

const countDownFrom = (num) => {
    if (num === 0) return
    console.log(num)
    countDownFrom(num - 1)
}

countDownFrom(10)

// Practical example. Taking data from a realtional database to make a "windows style menu"

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

const makeTree = (categories, parent) => {
    const node = {}
    categories
        .filter(c => c.parent === parent)
        .forEach(c => node[c.id] = 
            makeTree(categories, c.id))
    return node
}

console.log(
    JSON.stringify(
        makeTree(categories, null)
    , null, 2)
)

// Desired output - tree structure:

{
    animals: {
        mamals: {
            dogs: {
                chihuahua: null
                labrador: null
            },
            cats: {
                persian: null
                siamese: null
            }
        }
    }
}