Document 4 — Introducing Children Recursive Nesting

So far, every node has been simple. Now we make the structure slightly more interesting.

We will do two things:

• Add a child to an existing root node.
• Add a new root node and give that new node a child.

The traversal engine itself still does not change.

1. Add a Child to an Existing Node

Start with the existing customer node:

{
  "customer": {
    "name": "Keshav"
  },
  "order": {
    "id": "ORD-101"
  }
}

Now give customer another child: email.

{
  "customer": {
    "name": "Keshav",
    "email": "keshav@example.com"
  },
  "order": {
    "id": "ORD-101"
  }
}

2. Add a New Root with Its Own Child

Now add product at the root, and give it a child called code:

{
  "customer": {
    "name": "Keshav",
    "email": "keshav@example.com"
  },
  "order": {
    "id": "ORD-101"
  },
  "product": {
    "code": "P-100"
  }
}

3. Describe the New Structure with Instructions

{
  "customer": {
    "name": {
      "transform": "logPath"
    },
    "email": {
      "transform": "logPath"
    }
  },
  "order": {
    "id": {
      "transform": "logPath"
    }
  },
  "product": {
    "code": {
      "transform": "logPath"
    }
  }
}

Notice what happened. We did not add another traversal algorithm for children. The same traversal simply continues deeper into the source.

4. The Function Still Does Not Change

function logPath(value, path) {
  console.log("I am here in the tree:", path, value);
}

The function knows nothing about customer, email, product, or code. Those values come from the source at runtime.

5. The Traversal Reaches the New Locations

I am here in the tree: customer.name Keshav
I am here in the tree: customer.email keshav@example.com
I am here in the tree: order.id ORD-101
I am here in the tree: product.code P-100

The Point

The structure has become deeper, but the traversal has not become more complicated.