test.js

const categories =[  { id: 'E-commerce', parent: null },  { id: 'Electronics', parent: 'E-commerce' },  { id: 'Mobiles', parent: 'Electronics' },  { id: 'Laptops', parent: 'Electronics' },  { id: 'Camera', parent: 'Electronics' },  { id: 'Lifestyle', parent: 'E-commerce' },  { id: 'Clothing', parent: 'Lifestyle' },  { id: 'Footware', parent: 'Lifestyle' },  { id: 'Grooming', parent: 'Lifestyle' },  { id: 'Jewellery', parent: 'Lifestyle' },]

function Node(data) {
    this.data = data;
    this.children = [];
}


function solution(arr) {
  const n = arr.length
  if (n === 0) {
    return {}
  }
  const visited = Array(n).fill(false);
  const nullObjIndex = arr.findIndex( (o) => o.parent === null );
  visited[nullObjIndex] = true
  const nullObj = arr[nullObjIndex]
  var root = new Node(nullObj.id)
  buildTree(root, arr, visited)
  console.log(root)
  var result = {}
  result[root.data] = {}
  buildObject(root, result[root.data]);
  return result;
}

function buildTree(curr, arr, visited) {
  if (visited.reduce( (a,b) => a && b)) {
    return
  }
  for(let i = 0; i < arr.length; i++) {
    if(curr.data === arr[i].parent) {
      curr.children.push( new Node(arr[i].id) )
      visited[i] = true
    }
  }
  curr.children.map((child) => buildTree(child, arr, visited))
}

function buildObject(currNode, currObj) {
  currNode.children.forEach((child) => {
    currObj[child.data] = {}
    buildObject(child, currObj[child.data])
  })
}

console.log(solution(categories))