I have an array of objects and every objects has the fields id, parentId and position.
The position field stores the relative position of that item, so if I make a sort function like this:
object.sort((a, b) => {
if(a.position < b. position) return -1;
if(a.position > b. position) return 1;
return 0;
})
It ends up like this:
{id: 1, parentId: null, position: 0}
{id: 3, parentId: null, position: 1}
{id: 5, parentId: 1, position: 1}
{id: 6, parentId: 3, position: 1}
{id: 4, parentId: null, position: 2}
{id: 2, parentId: 1, position: 2}
How to check both parentId and position to end up like this?
{id: 1, parentId: null, position: 0}
{id: 5, parentId: 1, position: 1}
{id: 2, parentId: 1, position: 2}
{id: 3, parentId: null, position: 1}
{id: 6, parentId: 3, position: 1}
{id: 4, parentId: null, position: 2}
You could collect all nodes by their parentId and get the ordered result starting with null and by the ordered arrays.
const
getNodes = parent => (parents[parent] || [])
.sort((a, b) => a.position - b.position)
.flatMap(o => [o, ...getNodes(o.id)]),
data = [{ id: 1, parentId: null, position: 0 }, { id: 2, parentId: 1, position: 2 }, { id: 3, parentId: null, position: 1 }, { id: 6, parentId: 3, position: 1 }, { id: 4, parentId: null, position: 2 }, { id: 5, parentId: 1, position: 1 }],
parents = data.reduce((r, o) => ((r[o.parentId] ??= []).push(o), r), {}),
result = getNodes(null);
console.log(result);
console.log(parents);.as-console-wrapper { max-height: 100% !important; top: 0; }