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Marshal is the by far fastest Javascript validation and serialization implementation to marshal JSON-representable data from JSON objects to class instances to database records and vice versa, written in and for TypeScript. Marshal uses a JIT engine, generating highly optimized serialization functions on the fly. Marshal is an addition to JSON.parse(), not a replacement.

Marshal introduces the concept of decorating your entity class or class methods once with all necessary decorators (like type declaration, indices, and relations) using only Marshal's TypeScript decorators agnostic to any serialization target by saving only the meta data, and then use it everywhere: frontend, backend, CLI, database records, http-transport, rpc serialization, query parameter, DTOs, and database, including validations.


  • Fastest serialization and validation thanks to a JIT engine. It's the the by far fastest serialization library for both, Nodejs and browsers.
  • Supported types: String, Number, Boolean, Date, Moment.js, ArrayBuffer (binary), custom classes, Array, object maps, any.
  • Typed arrays: Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array
  • Cross referencing/Circular references using @f.forwardRef
  • Constructor support (required property can be placed in constructor) making it suitable for Typescript strict compiling
  • Validation: Built-in, custom class and inline validators
  • Decorated property values (e.g. JSON uses plain Array, class instance uses a custom Collection class)
  • Partial/Patch marshalling (ideal for serialising JSON Patch and the like)
  • Complex models with parent references
  • Support declaring method arguments and return type for method serialization
  • Implicit type detection as far as Typescript allows it technically
  • Supports getters
  • One decorator for all. Best and mist efficient UX possible, with full type hinting support
  • Soft type castings (so implicit cast from number -> string, if necessary)
  • NestJS validation pipe
  • MongoDB database abstraction and query builder with relation and join support


  • Add type support for: Map<T, K>, Set
  • Add more built-in validators
  • Support discriminators (union class types)
  • Add automatic tests IE11+ (help is welcome)



npm install @marcj/marshal reflect-metadata

Make sure you have experimentalDecorators and emitDecoratorMetadata enabled in tsconfig.json:

  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true

If you use Webpack's UglifyJsPlugin, make sure names are not mangled (mangle: false), which is the default. This is important to support constructor assignment. You can alternatively use asName() to hard code the constructor param names as strings.


import {
} from '@marcj/marshal';

class SubModel {
    @f label: string;

export enum Plan {

class SimpleModel {
    id: string = uuid();

    tags: string[] = [];

    @f.optional() //binary
    picture?: ArrayBuffer;

    type: number = 0;

    @f.enum(Plan, /*allowLabelsAsValue=*/ true)
    plan: Plan = Plan.DEFAULT;

    created: Date = new Date;

    children: SubModel[] = [];

    childrenMap: {[key: string]: SubModel} = {};

        @f.index().asName('name') //asName is required for minimized code
        public name: string
    ) {}

//data comes usually from files or http request
const instance = plainToClass(SimpleModel, {
    name: 'myName',
    tags: ['foo', 'bar'],
    plan: 'PRO',
    created: 'Sat Oct 13 2018 14:17:35 GMT+0200',
    children: [{label: 'foo'}],
    childrenMap: {'foo': {label: 'foo'}},
    SimpleModel {
      id: 'f2ee05ad-ca77-49ea-a571-8f0119e03038',
      name: 'myName',
      tags: ['foo', 'bar']
      type: 0,
      plan: 1,
      created: 2018-10-13T17:02:34.456Z,
      children: [ SubModel { label: 'foo' } ],
      childrenMap: { foo: SubModel { label: 'bar' } }


This library uses a JIT engine to convert data between class instances -> JSON objects and vice-versa. This means it builds JS functions in the background once you request a serialization for a certain class. The JIT code is then optimized further by the JS engine itself and then executed. By using as much information as possible during during build-time allows to achieve the best performance possible.

See bench.spec.ts for more details:

Tests were conducted on a Macbook Pro i9 with 2,9 GHz. On real server hardware with Linux this numbers are easily halved.

The class structure in question:

import {f, plainToClass} from "@marcj/marshal";

export class MarshalModel {
    @f ready?: boolean;

    @f.array(String) tags: string[] = [];

    @f priority: number = 0;

        @f public id: number,
        @f public name: string
    ) {

plainToClass(MarshalModel, {
    name: 'name',
    id: 1,
    tags: ['a', 'b', 'c'],
    priority: 5,
    ready: true,

Converting 100,000 elements from json to class instances (plainToClass) takes about 0.000184ms per item, in total 18ms.

Converting 100,000 elements from class instances to JSON objects (classToPlain) takes about 0.000089 per item, in total 9ms.

Compared to class-transformer:

  1. classToPlain takes 2748ms. Marshal is up to 30500% faster.
  2. plainToClass takes 2605ms. Marshal is up to 21700% faster.

Another comparison: Creating manually new class instances and assign properties is only barely faster.

const instance = new MarshalModel(1, 'name');
instance.tags = ['a', 'b', 'c'];
instance.priority = 5;
instance.ready = true;

Doing this 100,000 times takes 12.349ms instead of 18.483ms with Marshal.


Validation is equally JIT optimized and by far the fastest validator in its class. Validating 100.000 objects from the model above takes 0.000115ms per item, in total 12ms.

import {validate} from '@marcj/marshal';
const data = {
    name: 'name1',
    id: 1,
    tags: ['a', 2, 'c'],
    priority: 5,
    ready: true,
const errors = validate(MarshalModel)(data);

Bar Graph - Node 12.x



Once your have defined your entity (see above) using the @f decorators you can use one of Marshal's core methods to transform data.

Note: Class fields that aren't annotated either by @f or any other decorator won't be serialized. Their value will be dropped.


  • JSON object to class instance (plainToClass).

  • JSON object to mongo record (plainToMongo).

  • class instance to JSON object (classToPlain).

  • class instance to mongo record (classToMongo).

  • mongo record to class instance (mongoToClass).

  • mongo record to JSON object (mongoToPlain).

Note: 'JSON object' is not a string, but an object with valid JSON values, which can then be used to serialise to JSON string using JSON.stringify(classToPlain(SimpleModel, ...)).


You can validate incoming object literals or an class instance.

First make sure you have some validators attached to your fields you want to validate.

import 'jest';
import {f, validate, ValidationError, validatedPlainToClass, plainToClass} from '@marcj/marshal';

class Page {
    name: string;

    age: number;

const errors = validate(Page, {name: 'peter'});
expect(errors[0].message).toBe('Required value is undefined or null');
if (errors.length === 0) {
    const page = plainToClass(Page, {name: 'peter'});

//or do both at the same time and throw error if validations fails
const page = validatedPlainToClass(Page, {name: 'peter'});

You can also write custom validators

import {f, PropertyValidatorError, PropertyValidator} from '@marcj/marshal';

class MyCustomValidator implements PropertyValidator {
     validate<T>(value: any): PropertyValidatorError {
         if (value.length > 10) {
             return new PropertyValidatorError('too_long', 'Too long :()');

class Entity {
    name: string;

or inline validators

import {f, PropertyValidatorError} from '@marcj/marshal';

class Entity {
    @f.validator((value: any) => {
        if (value.length > 10) {
            return new PropertyValidatorError('too_long', 'Too long :()');
    name: string;

Partial serialization

Most of the time, you want to have full class instances so the internal state is always valid. However, if you have a patch mechanism, use JSON Patch, or just want to change one field value in the database, you might have the need to serialize only one field.

  • partialPlainToClass
  • partialClassToPlain
  • partialClassToMongo
  • partialPlainToMongo
  • partialMongoToPlain

@f decorator: define types

Class fields are annotated using mainly @f. You can define primitives, class mappings, relations between parents, and indices for the database (currently MongoDB).

Most of the time @f is able to detect the primitive type by reading the emitted meta data from TypeScript when you declared the type correctly in Typescript. However, @f provides additional chainable methods to let you further define the type. This duplication in defining the type is necessary since Typescript's reflection ability is only very rudimentary.

Example valid decoration:

import {f} from '@marcj/marshal';

class Page {
    @f.optional() //will be detected as String
    name?: string;

    @f.array(String) //will be detected as String array
    name: string[] = [];

    @f.map(String) //will be detected as String map
    name: {[name: string]: string} = {};

Example not valid decorators:

import {f} from '@marcj/marshal';

class Page {
    @f //can't be detected, you get an error with further instructions

More examples:

import {f, uuid} from '@marcj/marshal';
import * as moment from 'moment';

class MyModel {
    id: string = uuid();

    name?: string;

    created: Date = new Date;

    modified?: moment.Moment = moment();

Method annotation

You can also annotate class methods and method arguments. This can be useful for building custom RPC interfaces.

import {
    f, PartialField, argumentClassToPlain, argumentPlainToClass,
    methodResultClassToPlain, methodResultPlainToClass,
} from '@marcj/marshal';

class Config {
    name?: string;

    sub?: Config;

    prio: number = 0;

class Controller {
    @f.partial(Config) //this defines the return type.
    foo(name: string): PartialField<Config> {
        return {prio: 2, 'sub.name': name};

    @f //this register the function. `Config` type can be retrieve by TS reflection
    bar(config: Config): Config {
        config.name = 'peter';
        return config;

    @f.array(Number) //return type. Necessary to specify array, since `number[]` is not inferable
    another(@f.array(String) names: string[]): number[] {
        return [1, 2];

//from class to transport layer
const arg0 = argumentClassToPlain(Controller, 'foo', 0, 2); //'2'
const res = methodResultClassToPlain(Controller, 'foo', {'sub.name': 3}); //{'sub.name': '3'}

//from transport layer to 
const arg0 = argumentPlainToClass(Controller, 'bar', 0, {prio: '2'}); //Config {}
const res = methodResultPlainToClass(Controller, 'bar', {'sub': {name: 3}}); //Config {}


Instead of Date object you can use Moment if moment is installed.

In MongoDB it's stored as Date. In JSON its encoded as ISO8601 string.

import {f} from '@marcj/marshal';
import * as moment from 'moment';

class MyModel {
    created?: moment.Moment = moment();


exclude lets you exclude properties from a class in a certain direction. Per default it excludes to export to *toPlain and *toMongo. You can also use 'mongo' or 'plain' to have more control. Note: Fields that are not decorated with @f are not mapped and will be excluded per default.

import {f} from '@marcj/marshal';

class MyEntity {
    id: string;

    internalState: string;

    publicState: string;


@ParentReference together with @f is used for all *ToClass functions and allows you to have the parent from instance of class given in @f assigned as reference. Properties that used @ParentReference are automatically excluded in *ToPlain and *ToMongo functions.

import {f, ParentReference, plainToClass} from '@marcj/marshal';

class Page {
    name: string;

    children: Page[] = [];

    parent?: Page;

const root = plainToClass(Page, {
    name: 'Root',
    children: [
        {name: 'Child 1'},
        {name: 'Child 2'},

root.children[0].parent === root; //true

OnLoad(options?: {fullLoad?: boolean})

With @OnLoad you can register one or multiple callbacks for the onLoad lifetime event. The registered method is called when the class has been instantiated with the *ToClass functions.

If fullLoad is true, the callback is called when the whole chain of objects has been created, which means when all parents and siblings are fully initialised.

import {f, OnLoad} from '@marcj/marshal';
class Page {
    name: string;

    onLoad() {

Value decorator

decorated() lets you transform the actual class into something different. This is useful if you have in the actual class instance (plainToClass or mongoToClass) a wrapper for a certain property, for example string[] => ChildrenCollection.

import {f} from '@marcj/marshal';
class ChildrenCollection {

        public items: string[]
    ) {

    public add(item: string) {

class MyEntity {
    _id: string;

    //in *toMongo and *toPlain is children the value of ChildrenCollection::items
    children: ChildrenCollection = new ChildrenCollection([]);

ChildrenCollection is now always used in *toClass calls. The constructor of ChildrenCollection receives the actual value as first argument.

import {classToPlain} from '@marcj/marshal';

const entity = new MyEntity();
const result = classToPlain(MyEntity, entity);
result = {
    id: 'abcde',
    children: ['Foo', 'Bar']

If you read values from mongo or plain to class (mongoToClass, plainToClass) your decorator will be used again and receives as first argument the actual property value:

import {classToPlain} from '@marcj/marshal';

const entity = plainToClass(MyEntity, {
    id: 'abcde',
    children: ['Foo', 'Bar']
entity.children instanceof ChildrenCollection; //true

//so you can work with it again

Patch serialization

If you work with rather big entities, your probably want to utilise some kind of patch mechanism. Marshal supports to transform partial objects as well with deep path properties. All of following partial* methods maintain the structure of your object and only transform the value. We resolve the dot symbol to retrieve type information, so you can use this also in combination with JSON-Patch.


import {partialPlainToClass} from '@marcj/marshal';

const converted = partialPlainToClass(SimpleModel, {
    id: 'abcde',
    ['childrenMap.item.label']: 3 

converted['childrenMap.item.label'] === '3' //true

const i2 = partialPlainToClass(SimpleModel, {
    'children': [{'label': 3}]

partialClassToPlain / partialClassToMongo

toPlain and toMongo differ in the way, that latter will transform mongoId) and uuid() in different way, suitable for Mongo's binary storage.

import {partialClassToPlain} from '@marcj/marshal';

const plain = partialClassToPlain(SimpleModel, {
    'children.0': i.children[0],
    'stringChildrenCollection': new StringCollectionWrapper(['Foo', 'Bar']),
    'childrenCollection': new CollectionWrapper([new SubModel('Bar3')]),
    'childrenCollection.1': new SubModel('Bar4'),
    'stringChildrenCollection.0': 'Bar2',
    'childrenCollection.2.label': 'Bar5',

expect(plain['stringChildrenCollection']).toEqual(['Foo', 'Bar']);
expect(plain['childrenCollection']).toEqual([{label: 'Bar3'}]);
expect(plain['childrenCollection.1']).toEqual({label: 'Bar4'});

Custom serialization target

In Marshal everything is compiled down to a highly optimized JS function. That means when you want to add another serialization target, you have to write compiler templates. But it sounds scarier than it is. Here's an example on how to convert a date to a ISO format for JSON transportation.

import {registerConverterCompiler} from '@marcj/marshal';

//from class instance values to your MyTarget type, which will be a string here
registerConverterCompiler('class', 'MyTarget', 'date', (setter: string, accessor: string) => {
    return `${setter} = ${accessor}.toJSON();`;

//from your MyTarget type to class instance values 
registerConverterCompiler('MyTarget', 'class', 'date', (setter: string, accessor: string) => {
    return `${setter} = new Date(${accessor});`;

To use your custom target, you can use these JIT functions:

import {ClassType, getClassName} from "@marcj/estdlib";
import {createClassToXFunction, createXToClassFunction} from '@marcj/marshal';
export function classToMyTarget<T>(classType: ClassType<T>, instance: T): any {
    if (!(instance instanceof classType)) {
        throw new Error(`Could not classToMyTarget since target is not a class instance of ${getClassName(classType)}`);
    return createClassToXFunction(classType, 'MyTarget')(instance);

export function myTargetToClass<T>(classType: ClassType<T>, record: any, parents?: any[]): T {
    return createXToClassFunction(classType, 'MyTarget')(record, parents);

See compiler templates of mongodb and its user facing API to get more examples.

Mongo ORM / Database abstraction

Marshal's MongoDB database abstraction makes it super easy to retrieve and store data from and into your MongoDB. We make sure the data from your JSON or class instance is correctly converted to MongoDB specific types and inserted IDs are applied to your class instance.

See documentation for more information;

npm install @marcj/marshal-mongo
import {Database, Connection} from "@marcj/marshal-mongo";

const database = new Database(new Connection('localhost', 'mydb', 'username', 'password'));

const instance = new SimpleModel('My model');
await database.add(instance);

const list = await database.query(SimpleModel).find();
const oneItem = await database.query(SimpleModel).filter({id: 'f2ee05ad-ca77-49ea-a571-8f0119e03038'}).findOne();

More documention to come.

NestJS / Express

It's super common to accept data from a frontend via HTTP, transform the body into your class instance, work with it, and then store that data in your MongoDB or somewhere else. With Marshal this scenario is super simple and you do not need any manual transformations.

npm install @marcj/marshal-nest
import {
    Controller, Get, Param, Post, Body
} from '@nestjs/common';

import {Database, Connection} from "@marcj/marshal-mongo";
import {SimpleModel} from "@marcj/marshal/tests/entities";
import {classToPlain} from "@marcj/marshal";
import {ValidationPipe} from "@marcj/marshal-nest";

class MyController {
    private database = new Database(new Connection('localhost', 'testing');

    async save(
        @Body(ValidationPipe({transform: true})) body: SimpleModel,
    ) {
        body instanceof SimpleModel; // true;
        await this.database.add(body);

        return body.id;

    async get(@Param('id') id: string) {
        const instance = await this.database.query(SimpleModel).filter({_id: id}).findOne();

        return classToPlain(SimpleModel, instance);

Development of this package

How to release:

# remove packages/*/lib folders
# develop changes, run tests
./node_modules/.bin/jest --coverage

# build TS
lerna run tsc

# publish
lerna publish patch

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