durable-execution-sdk-js.createclassserdes.md

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createClassSerdes() function

This API is provided as a beta preview for developers and may change based on feedback that we receive. Do not use this API in a production environment.

Creates a Serdes for a specific class that preserves the class type. This implementation is a basic class wrapper and does not support any complex class structures. If you need custom serialization, it is recommended to create your own custom serdes.

Signature:

export declare function createClassSerdes<T extends object>(
  cls: new () => T,
): Serdes<T>;

Parameters

Parameter	Type	Description
cls	new () => T	The class constructor (must have no required parameters)

Returns:

Serdes<T>

A Serdes that maintains the class type during serialization/deserialization

Example

class User {
  name: string = "";
  age: number = 0;

  greet() {
    return `Hello, ${this.name}`;
  }
}

const userSerdes = createClassSerdes(User);

// In a durable function:
const user = await context.step(
  "create-user",
  async () => {
    const u = new User();
    u.name = "Alice";
    u.age = 30;
    return u;
  },
  { serdes: userSerdes },
);

console.log(user.greet()); // "Hello, Alice" - methods are preserved

Limitations: - Class instances becomes plain objects and loses all class information - Constructor must have no parameters - Constructor side-effects will re-run during deserialization - Private fields (#field) cannot be serialized - Getters/setters are not preserved - Nested class instances lose their prototype

For classes with Date properties, use createClassSerdesWithDates instead.