index/classes/PayloadWalkerWithDeduplication.md

Payload Walker with Deduplication

Recursively walks through object payloads to extract events while deduplicating by a key (e.g., transactionId, eventId). Prevents duplicate processing of the same event across multiple payload traversals.

Used to find events nested at various depths in WebSocket payloads.

Features:

• Recursive depth limiting (prevents DoS from circular structures)
• WeakSet tracking to prevent infinite loops on circular references
• Configurable deduplication key
• Callback-based event processing

Example

// Test case: Recursive payload walking with deduplication
const walker = new PayloadWalkerWithDeduplication<{ id: string; value: number }>(
  (obj) => {
    // Extraction predicate: return event if found
    return obj.id && obj.value ? { id: obj.id, value: obj.value } : null;
  },
  (event) => event.id // Deduplication key
);

// First walk - extracts new events
const events1 = walker.walk({
  Data: { id: 'e1', value: 100 },
  nested: { id: 'e2', value: 200 }
});
console.assert(events1.length === 2);

// Second walk - skips already seen events
const events2 = walker.walk({
  Data: { id: 'e1', value: 999 }, // Already seen, skipped
  other: { id: 'e3', value: 300 }  // New, included
});
console.assert(events2.length === 1);
console.assert(events2[0].id === 'e3');

// Reset deduplication to reprocess all events
walker.reset();
const events3 = walker.walk({ Data: { id: 'e1', value: 100 } });
console.assert(events3.length === 1); // e1 is processed again

Since

6.6.0

Type Parameters

Type Parameter	Description
T	Event type being extracted

Constructors

Constructor

new PayloadWalkerWithDeduplication<T>(extractor, dedupeKeyFn, maxDepth?): PayloadWalkerWithDeduplication<T>

Parameters

Parameter	Type
extractor	(obj) => T | null
dedupeKeyFn	(event) => string
maxDepth?	number

Returns

PayloadWalkerWithDeduplication<T>

Methods

getSeenCount()

getSeenCount(): number

Get count of deduplicated events

Returns

number

Number of unique events seen so far

---

reset()

reset(): void

Reset deduplication state to reprocess all events

Returns

void

---

walk()

walk(payload): T[]

Walk through a payload and extract events

Parameters

Parameter	Type	Description
payload	unknown	Root object to traverse

Returns

T[]

Array of extracted events not previously seen