Create a nested array of objects with id and parentId pointers

formatNested.ts

export const formatNested = function (flatArray: any[], id: any, parentId: any): Array<any> {
	const collection: Array<any> = [];
	flatArray.forEach((item) => (collection[item[id]] = { ...item, children: [] }));
	const result: Array<any> = [];
	flatArray.forEach((item) => {
		if (item[parentId]) {
			if (collection[item[parentId]]) {
				collection[item[parentId]].children.push(collection[item[id]]);
			}
		} else {
			result.push(collection[item[id]]);
		}
	});
	return result;
};
  
// formatNested(collection, 'id', 'parent');