Build tree hierarchy by ancestors

[alexanderpa]

It would be great to have possibility to build hierarchy tree not only by parent reference but with ancestors also.

[joaonuno]

Can you please share an example?

[alexanderpa]

Yes, sure. For example you have flat list of nodes:
[
{ id: 1, name: 'first', ancestors: [] },
{ id: 2, name: 'second', ancestors: [1] },
{ id: 3, name: 'third', ancestors: [1,2] },
...
]

This list should be converted to:

{
id: 1,
name: 'first',
ancestors: [],
children: [
{
id: 2,
name: 'second',
ancestors: [1],
children: [...]
}
]
}

[joaonuno]

It seems that's not a tree, because a tree node should have just one ancestor (or parent) right?
Where would you represent node 3 in your example? It is a child of both nodes 1 and 2?

[alexanderpa]

node3 should be the child node of node2

[alexanderpa]

you could see an example how this tree structure stored in mongodb https://docs.mongodb.org/manual/tutorial/model-tree-structures-with-ancestors-array/

[joaonuno]

ok, got it, that's an optimization for fast path retrieval. For tree construction, all that's necessary is the last ancestor.

I guess that could be supported if instead of using a parent property we could specify a function to get the parent and in this case the developer could pass a function to get the last ancestor.

Something like:

flatToNested = new FlatToNested({
    // The function to get the parent id
    parent: function (node) {
        return node.ancestors[node.ancestors.length - 1];
    }
}});

What do you think?

[alexanderpa]

Looks good to me.