docs/guide/javascript/references.md

---
title: References
sidebar_position: 50
id: references
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---

By default Fory treats every value as a separate copy — if the same object appears in two fields it gets serialized twice, and after deserialization you get two independent copies. Enable reference tracking when:

- the same object instance is referenced from multiple places in the graph
- your data contains a circular structure (e.g. a node that points to itself)
- object identity must be preserved after a round trip

Leave reference tracking off for plain tree-shaped data; it adds a small overhead.

## Step 1: Enable Reference Tracking on the `Fory` Instance

```ts
const fory = new Fory({ ref: true });
```

## Step 2: Mark the Fields That Can Have Shared or Circular References

For each field whose value may be shared or circular, call `.setTrackingRef(true)` on the field's schema:

```ts
const nodeType = Type.struct("example.node", {
  value: Type.string(),
  next: Type.struct("example.node").setNullable(true).setTrackingRef(true),
});
```

You need **both** the global flag and the field-level flag. Missing either one results in values being copied rather than referenced.

## Circular self-reference example

```ts
import Fory, { Type } from "@apache-fory/core";

const nodeType = Type.struct("example.node", {
  name: Type.string(),
  selfRef: Type.struct("example.node").setNullable(true).setTrackingRef(true),
});

const fory = new Fory({ ref: true });
const { serialize, deserialize } = fory.register(nodeType);

const node: any = { name: "root", selfRef: null };
node.selfRef = node;

const copy = deserialize(serialize(node));
console.log(copy.selfRef === copy); // true
```

## Shared nested reference example

```ts
const innerType = Type.struct(501, {
  value: Type.string(),
});

const outerType = Type.struct(502, {
  left: Type.struct(501).setNullable(true).setTrackingRef(true),
  right: Type.struct(501).setNullable(true).setTrackingRef(true),
});

const fory = new Fory({ ref: true });
const { serialize, deserialize } = fory.register(outerType);

const shared = { value: "same-object" };
const copy = deserialize(serialize({ left: shared, right: shared }));
console.log(copy.left === copy.right); // true
```

## When to enable it

Enable reference tracking when:

- the same object instance is reused in multiple fields
- your graph can be cyclic
- identity preservation matters after deserialization

Leave it disabled when:

- the data is a plain tree
- you want the lowest overhead
- object identity does not matter

## Cross-Language Note

Reference tracking is part of the Fory binary protocol and works across runtimes. Both sides must enable reference tracking and mark the same fields as reference-tracked for the behavior to be consistent.

## Related Topics

- [Basic Serialization](basic-serialization.md)
- [Schema Evolution](schema-evolution.md)
- [Cross-Language](cross-language.md)