JSFiddle - React, Tailwind, and code Playground

JavaScript

list = [
  {
    id: 1,
    title: 'home',
    parent: null
  },
  {
    id: 2,
    title: 'about',
    parent: null
  },
  {
    id: 3,
    title: 'team',
    parent: 2
  },
  {
    id: 4,
    title: 'company',
    parent: 2
  }
]

function treeify(list, idAttr, parentAttr, childrenAttr) {
    if (!idAttr) idAttr = 'id';
    if (!parentAttr) parentAttr = 'parent';
    if (!childrenAttr) childrenAttr = 'children';
    var treeList = [];
    var lookup = {};
    list.forEach(function(obj) {
        lookup[obj[idAttr]] = obj;
        obj[childrenAttr] = [];
    });
    list.forEach(function(obj) {
        if (obj[parentAttr] != null) {
            lookup[obj[parentAttr]][childrenAttr].push(obj);
        } else {
            treeList.push(obj);
        }
    });
    return treeList;
};

console.log(JSON.stringify(treeify(list)));