docs/guide/javascript/basic-serialization.md

---
title: Basic Serialization
sidebar_position: 1
id: basic_serialization
license: |
  Licensed to the Apache Software Foundation (ASF) under one or more
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  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
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---

This guide covers the core serialization APIs in Apache Fory JavaScript.

## Create a `Fory` Instance

```ts
import Fory from "@apache-fory/core";

const fory = new Fory();
```

Create one instance, register your schemas, and reuse it. Fory caches the generated serializers after the first `register` call, so recreating it on every request wastes that work.

## Define a Schema with `Type.struct`

The most common path is to define a schema and register it.

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

const accountType = Type.struct(
  { typeName: "example.account" },
  {
    id: Type.int64(),
    owner: Type.string(),
    active: Type.bool(),
    nickname: Type.string().setNullable(true),
  },
);

const fory = new Fory();
const { serialize, deserialize } = fory.register(accountType);
```

## Serialize and Deserialize

```ts
const bytes = serialize({
  id: 42n,
  owner: "Alice",
  active: true,
  nickname: null,
});

const value = deserialize(bytes);
console.log(value);
// { id: 42n, owner: 'Alice', active: true, nickname: null }
```

The returned `bytes` value is a `Uint8Array`/platform buffer and can be sent over the network or written to storage.

## Root-Level Dynamic Serialization

`Fory` can also serialize dynamic root values without first binding a schema-specific serializer.

```ts
const fory = new Fory();

const bytes = fory.serialize(
  new Map([
    ["name", "Alice"],
    ["age", 30],
  ]),
);

const value = fory.deserialize(bytes);
```

This is convenient for dynamic payloads, but explicit schemas are usually better for stable interfaces and cross-language contracts.

## Primitive Values

```ts
const fory = new Fory();

fory.deserialize(fory.serialize(true));
// true

fory.deserialize(fory.serialize("hello"));
// 'hello'

fory.deserialize(fory.serialize(123));
// 123

fory.deserialize(fory.serialize(123n));
// 123n

fory.deserialize(fory.serialize(new Date("2021-10-20T09:13:00Z")));
// Date
```

### Number and `bigint`

JavaScript `number` is a 64-bit float, which cannot exactly represent all 64-bit integers. For cross-language contracts or anywhere exact integer sizes matter, use explicit field types in your schema:

- `Type.int32()` — 32-bit integer; use JavaScript `number`
- `Type.int64()` — 64-bit integer; use JavaScript `bigint`
- `Type.float32()` / `Type.float64()` — floating-point

Dynamic root serialization (calling `fory.serialize(someNumber)` without a schema) will infer a type, but the inferred type is not guaranteed by the API. Use a schema for any stable contract.

## Arrays, Maps, and Sets

```ts
const inventoryType = Type.struct("example.inventory", {
  tags: Type.list(Type.string()),
  counts: Type.map(Type.string(), Type.int32()),
  labels: Type.set(Type.string()),
});

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

const bytes = serialize({
  tags: ["hot", "new"],
  counts: new Map([
    ["apple", 3],
    ["pear", 8],
  ]),
  labels: new Set(["featured", "seasonal"]),
});

const value = deserialize(bytes);
```

## Nested Structs

```ts
const addressType = Type.struct("example.address", {
  city: Type.string(),
  country: Type.string(),
});

const userType = Type.struct("example.user", {
  name: Type.string(),
  address: Type.struct("example.address", {
    city: Type.string(),
    country: Type.string(),
  }),
});

const fory = new Fory();
const { serialize, deserialize } = fory.register(userType);

const bytes = serialize({
  name: "Alice",
  address: { city: "Hangzhou", country: "CN" },
});

const user = deserialize(bytes);
```

If a nested value can be missing, mark it nullable:

```ts
const wrapperType = Type.struct("example.wrapper", {
  child: Type.struct("example.child", {
    name: Type.string(),
  }).setNullable(true),
});
```

## Decorator-Based Registration

TypeScript decorators are also supported.

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

@Type.struct("example.user")
class User {
  @Type.int64()
  id!: bigint;

  @Type.string()
  name!: string;
}

const fory = new Fory();
const { serialize, deserialize } = fory.register(User);

const user = new User();
user.id = 1n;
user.name = "Alice";

const copy = deserialize(serialize(user));
console.log(copy instanceof User); // true
```

## Nullability

Field nullability is explicit in schema-based structs.

```ts
const nullableType = Type.struct("example.optional_user", {
  name: Type.string(),
  email: Type.string().setNullable(true),
});
```

If a field is not marked nullable and you try to write `null`, serialization throws.

## Debugging Generated Code

You can inspect generated serializer code with `hooks.afterCodeGenerated`.

```ts
const fory = new Fory({
  hooks: {
    afterCodeGenerated(code) {
      console.log(code);
      return code;
    },
  },
});
```

This is useful when debugging schema behavior, field ordering, or generated fast paths.

## Related Topics

- [Type Registration](type-registration.md)
- [Supported Types](supported-types.md)
- [References](references.md)