Is there an easy way to construct a structured object(with nested object) from an array providing level/node informations?

Question

I work with a weird javascript array structured like this: ["node1", "alias1", 1, "node2", "alias2", 2, "node3", "alias3", 2, "node4", "alias4", 1, "node5", "alias5", 2]

This array represent a structured tree(seem to represent...), there is a triplet of information on each node: the node name, the alias and the hierarchy level. To structure this array into a interesting object I need to put all children under their parent, the parent is the one that have "1" in the hierarchy level and the children have "2" in hierarchy level.

So I want to transform this array into this object :

[
   {
      "node_name":"node1",
      "alias":"alias1",
      "children":[
         {
            "node_name":"node2",
            "alias":"alias2"
         },
         {
            "node_name":"node3",
            "alias":"alias3"
         }
      ]
   },
   {
      "node_name":"node4",
      "alias":"alias4",
      "children":[
         {
            "node_name":"node5",
            "alias":"alias5"
         }
      ]
   }
]

I could make it with hands a construct somethings big and unoptimal, but before I try anything I want to know if there is something more simple, something that already exist that could help me to do this transformation.

PS:

I can't use non-native javascript, so I can't use external library, I have to solve this problem on my browser console.
I could try to help myself with this topic but in this case there is a link between parent and children by parentId, but in my case there no parentId neither in parent object nor in children object

Please share original data. It is not clear how the array items are grouped in the output json — JohnPan, Apr 12 '21 at 13:50

score 2 · Accepted Answer · answered Apr 12 '21 at 13:54

You could take an array for keeping the last inserted node for the level.

const
    data = ['node1', 'alias1', 1, 'node2', 'alias2', 2, 'node3', 'alias3', 2, 'node4', 'alias4', 1, 'node5', 'alias5', 2],
    result = [],
    levels = [{ children: result }];

for (let i = 0; i < data.length; i += 3) {
    const
        node_name = data[i],
        alias = data[i + 1],
        level = data[i + 2] - 1;
        
    (levels[level].children ??= []).push(levels[level + 1] = { node_name, alias });
}

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

It's working perfectly, thanks a lot. perfect. – bosskay972 Apr 12 '21 at 14:02 — bosskay972, Apr 12 '21 at 14:02

Is there an easy way to construct a structured object(with nested object) from an array providing level/node informations?

1 Answers1