Normalize nested API entities

Turn nested documents into stable entity maps and ordered ID references.

MediumJavaScript Data Modeling

50 min0% acceptance

Description

Implement normalizeDocuments(documents). Return documentIds, documentsById, usersById, and attachmentsById; replace nested owners and attachments with IDs; preserve root and attachment order; deduplicate shared entities with first occurrence winning; and always return fresh containers.

Requirements

Export a callable normalizeDocuments function from src/App.js.
Return document, user, and attachment maps keyed by each entity ID.
Store normalized documents as id, title, ownerId, and attachmentIds.
Store a shared owner or attachment once and reference the same ID everywhere.
Preserve input document order in documentIds and nested order in attachmentIds.
Keep the first occurrence when a later entity repeats an ID with different data.
Return four distinct empty containers for an empty document array.
Create new maps, arrays, and normalized entity records on every invocation.
Do not mutate documents, owners, attachments, or their arrays.

Shared owner

Input

Two documents contain owner u1

Expected output

Both documents reference ownerId u1 and usersById contains one u1

Explanation

Shared nested records become one canonical entity.

Conflicting duplicate

Input

Later owner u1 has a different name

Expected output

The first u1 name remains

Explanation

First occurrence wins deterministically across conflicting shared entities.

Constraints

Every entity has a nonempty string ID
Owners and attachments retain only id and name
Duplicate root document IDs also use first occurrence

Hints

Hint 1

Walk documents once and insert into each map only when the ID is not already present.

Hint 2

Build attachmentIds while visiting a document's attachments in order.

Hint 3

Construct normalized records explicitly instead of deleting fields from input objects.

JavaScriptnormalizationentity maps