How to recursive loop json with relationship and convert to object?

Question

I have this json data which I need to convert into an object. The json has a parent/child relationship instead of actual children object in the parent object.

{
    "queryType": "tree",
    "queryResultType": "workItemLink",
    "workItemRelations": [
        {
            "rel": null,
            "source": null,
            "target": {
                "id": 1166167,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1166167"
            }
        },
        {
            "rel": "System.LinkTypes.Hierarchy-Forward",
            "source": {
                "id": 1166167,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1166167"
            },
            "target": {
                "id": 1167481,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1167481"
            }
        },
        {
            "rel": "System.LinkTypes.Hierarchy-Forward",
            "source": {
                "id": 1167481,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1167481"
            },
            "target": {
                "id": 1234896,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1234896"
            }
        }
    ]
}

What I've done so far. Please note that the code below is not the actual code but are snippets I took from the actual code for simplicity.

import axios from 'axios';

interface Item {
    id: number;
    children: Item[];
}

interface WiqlResponse {
    queryType: string;
    queryResultType: string;
    asOf: string;
    workItemRelations: Array<{
        rel: string;
        source: { id: number; url: string } | null;
        target: { id: number; url: string };
    }>
}

export async function getWiql(wiql: string): Promise<WiqlResponse> {
    const response = await axios.get<WiqlResponse>(`/org/_apis/wit/wiql/${wiql}?api-version=7.1`);
    return response.data;
}

export async function main() {

    getWiql('123123213').then(wiqlResponse => {

        // Get all parent work items
        for (const pRel of wiqlResponse.workItemRelations.filter(r => r.rel == null)) {

            let childs: Item[] = [];
            // Get all children of this parent
            for (const cRel of wiqlResponse.workItemRelations.filter(r => r.source?.id == pRel.target.id)) {
                let child: Item = {
                    id: cRel.target.id,
                    children: []
                };
                childs.push(child);
            }
            let parent: Item = {
                id: pRel.target.id,
                children: childs
            };
        }
    });

}

The code above will work up to level 2 only but if you look closely at the json data, it has 3 level and could be more depending on the data from the source.

How can I recursively check if there are still child items?

EDIT: Here's a sample code that can be run without axios.

interface Item {
    id: number;
    children: Item[];
}

interface WiqlResponse {
    workItemRelations: Array<{
        rel: string | null;
        source: { id: number; url: string } | null;
        target: { id: number; url: string };
    }>
}

const wiqlResponse: WiqlResponse = {

    "workItemRelations": [
        {
            "rel": null,
            "source": null,
            "target": {
                "id": 1166167,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1166167"
            }
        },
        {
            "rel": "System.LinkTypes.Hierarchy-Forward",
            "source": {
                "id": 1166167,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1166167"
            },
            "target": {
                "id": 1167481,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1167481"
            }
        },
        {
            "rel": "System.LinkTypes.Hierarchy-Forward",
            "source": {
                "id": 1167481,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1167481"
            },
            "target": {
                "id": 1234896,
                "url": "https://dev.azure.com/org/_apis/wit/workItems/1234896"
            }
        }
    ]
};


export async function main() {

  console.log('wiqlResponse: ', wiqlResponse);
    let items: Item[] = [];

        // Get all parent work items
        for (const pRel of wiqlResponse.workItemRelations.filter(r => r.rel == null)) {

            let childs: Item[] = [];
            // Get all children of this parent
            for (const cRel of wiqlResponse.workItemRelations.filter(r => r.source?.id == pRel.target.id)) {
                let child: Item = {
                    id: cRel.target.id,
                    children: []
                };
                childs.push(child);
            }
            let parent: Item = {
                id: pRel.target.id,
                children: childs
            };

      items.push(parent);
        }

    console.log('items:', JSON.stringify(items));
}

main();

EDIT: Apologies for not explaining the relationship of the json data.

The json provides a relationship between source and target. The target is a top most parent if it doesn't have a source. If the relationship has both source and target, the target is the child of the source.

EDIT: Adding the expected result for clarity. Again my apologies for not being concise the first time.

The expected result should be:

[
  {
    "id": 1166167,
    "children": [
      {
        "id": 1167481,
        "children": [
          {
            "id": 1234896,
            "children": []
          }
        ]
      }
    ]
  }
]

Answer 1 · 2025-11-25 01:05:04Z

Given your updated example, the following should work:

const itemMap: Record<number, Item> = {}
let items: Item[] = []
wiqlResponse.workItemRelations.forEach(i => itemMap[i.target.id] = { id: i.target.id, children: [] });
wiqlResponse.workItemRelations.forEach(i => {
    const sourceId = i.source?.id;
    if (!sourceId) {
        items.push(itemMap[i.target.id]);
        return;
    }        
    itemMap[sourceId].children.push(itemMap[i.target.id])
});
console.log('items:', JSON.stringify(items));

see this Playground link.

which logs [{"id":1166167,"children":[{"id":1167481,"children":[{"id":1234896,"children":[]}]}]}] as expected.

It basically creates all the items first with empty children, and stores them in a map keyed by id. Then it goes back through the list of relations and looks up the items to augment their children arrays.

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How to recursive loop json with relationship and convert to object?

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How to recursive loop json with relationship and convert to object?

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