typescript-json-serializer

A typescript library to deserialize json into typescript classes and serialize classes into json.

Summary

1. Installation
2. Usage
3. API
4. Development
5. Thanks to

Installation

npm install typescript-json-serializer --save
# or
yarn add typescript-json-serializer

You also need to set experimentalDecorators and emitDecoratorMetadata to true into the tsconfig.json file.

For example:

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

Usage

import { JsonSerializer, throwError } from 'typescript-json-serializer';

import { json } from '../json/data';
import { Organization } from '../models/organization';

// Instantiate a default serializer
const defaultSerializer = new JsonSerializer();

// Or you can instantiate a serializer with your custom options
const customSerializer = new JsonSerializer({
    // Throw errors instead of logging
    errorCallback: throwError,

    // Allow all nullish values
    nullishPolicy: {
        undefined: 'allow',
        null: 'allow'
    },

    // Disallow additional properties (non JsonProperty)
    additionalPropertiesPolicy: 'disallow',

    // e.g. if all the properties in the json object are prefixed by '_'
    formatPropertyName: (propertyName: string) => `_${propertyName}`,
})

// Deserialize
const organization = defaultSerializer.deserialize(json, Organization);

// Serialize
const data = defaultSerializer.serialize(organization);

Examples

Classes

// Import decorators from library
import { JsonObject, JsonProperty } from 'typescript-json-serializer';

// Enums
export enum Gender {
    Female,
    Male,
    Other
}

export enum Status {
    Alive = 'Alive',
    Sick = 'Sick',
    DeadAndAlive = 'Dead and alive',
    Dead = 'Dead'
}

// Create a JsonObject class: LivingBeing

// JsonObject decorator
@JsonObject()
export class LivingBeing {

    /** The living being id (PK) */
    @JsonProperty() id: number;
}


// Create a JsonObject class that extends LivingBeing: Human

@JsonObject()
export class Human extends LivingBeing {
    constructor(
        // This comment works
        // Override LivingBeing id property name
        // and set required to true
        @JsonProperty({name: 'humanId', required: true})
        public id: number,
        @JsonProperty() public name: string,
        @JsonProperty() public gender: Gender,
        /** This comment works */
        @JsonProperty() public readonly birthDate: Date
    ) {
        super();
        this.id = id;
    }
}


// Create a JsonObject class: PhoneNumber

@JsonObject()
export class PhoneNumber {
    @JsonProperty() countryCode: string;
    @JsonProperty() value: string;
}


// Create a JsonObject class that extends Human: Employee

@JsonObject()
export class Employee extends Human {
    /** The employee's email */
    @JsonProperty({required: true}) email: string;

    /** Predicate function to determine if the property type
      * is PhoneNumber or a primitive type */
    @JsonProperty({
        type: property => {
            if (property && property.value !== undefined) {
                return PhoneNumber;
            }
        }
    })
    phoneNumber: PhoneNumber | string;

    constructor(
        public name: string,
        // Override human id property name
        // (keep the require to true from Human id)
        @JsonProperty('employeeId') public id: number,
        public gender: Gender,
        public birthDate: Date
    ) {
        super(name, id, gender, birthDate);
    }
}


// Create a JsonObject class that extends LivingBeing: Animal

@JsonObject()
export class Animal extends LivingBeing {
    @JsonProperty() name: string | undefined;
    @JsonProperty() birthDate: Date;
    @JsonProperty() numberOfPaws: number;
    @JsonProperty() gender: Gender;

    // Enum value (string)
    @JsonProperty() status: Status;

    // Specify the property name of json property if needed
    @JsonProperty('childrenIdentifiers')
    childrenIds: Array<number>;

    constructor(name: string | undefined) {
        super();
        this.name = name;
    }

}


// Create a JsonObject class that extends Animal (which extends LivingBeing): Panther

@JsonObject()
export class Panther extends Animal {

    @JsonProperty() color: string;

    // JsonProperty directly inside the constructor
    // for property parameters
    public constructor(
        name: string | undefined,
        @JsonProperty() public isSpeckled: boolean
    ) {
        super(name);
    }

}


// Create a JsonObject class that extends Animal (which extends LivingBeing): Snake

// When the library instatiates a class during deserilization it does not know the constructor params value
// so you need to specify them.
// To ways are available
// - by passing default value to those params in the constructor
// - by passing the `constructorParams` options to `JsonObject` (see below); it allows to keep clean constructor
@JsonObject({ constructorParams: [{}] })
export class Snake extends Animal {

    @JsonProperty() isPoisonous: boolean;

    public constructor(args: { name: string | undefined; isPoisonous: boolean }) {
        super(args.name);
        this.isPoisonous = args.isPoisonous;
    }

}


// Create a JsonObject empty class that extends Animal (which extends LivingBeing): UnknownAnimal

@JsonObject()
export class UnknownAnimal extends Animal {
    public constructor(name: string) {
        super(name);
    }
}


// Create a JsonObject class: Zoo

// Function to transform coordinates into an array
const coordinatesToArray = (coordinates: {
    x: number;
    y: number;
    z: number;
}): Array<number> => {
    return Object.values(coordinates);
};

// Function to transform an array into coordinates
const arrayToCoordinates = (array: Array<number>): {
    x: number;
    y: number;
    z: number
} => {
    return {
        x: array[0],
        y: array[1],
        z: array[2]
    };
};

// A predicate function use to determine what is the
// right type of the data (Snake or Panther)
const snakeOrPanther = animal => {
    return animal && animal['isPoisonous'] !== undefined
        ? Snake
        : Panther;
};

@JsonObject()
export class Zoo {

    // Here you do not need to specify the type
    // inside the decorator
    @JsonProperty() boss: Employee;

    @JsonProperty() city: string;
    @JsonProperty() country: string;

    // Property with transform functions executed respectively
    // on serialize and on deserialize
    @JsonProperty({
        beforeDeserialize: arrayToCoordinates,
        afterSerialize: coordinatesToArray
    })
    coordinates: { x: number; y: number; z: number };

    // Possibly undefined Set of none-basic type elements
    @JsonProperty({ type: Employee, dataStructure: 'set' })
    employees: Set<Employee> | undefined;

    @JsonProperty() id: number;
    @JsonProperty() name: string;

    // Array of none-basic type elements where you need to
    // specify the name of the json property
    // and use the predicate function to cast the deserialized
    // object into the correct child class
    @JsonProperty({ name: 'Animals', type: snakeOrPanther })
    animals: Array<Animal>;

    // Property that can be Panther or Snake type
    // Use again the predicate function
    @JsonProperty({ type: snakeOrPanther })
    mascot: Panther | Snake;

    // Dictionary of empty child classes
    @JsonProperty({ dataStructure: 'dictionary', type: UnknownAnimal })
    unknownAnimals: { [id: string]: UnknownAnimal };

    // Map of array of PhoneNumber or string
    @JsonProperty({
        type: property => {
            if (property?.value !== undefined) {
                return PhoneNumber;
            }
        }
    })
    phoneBook: Map<string, Array<PhoneNumber | string>>;

    // Property which will be not serialized and deserialized
    // but event accessible and editable from Zoo class.
    public isFree: boolean = true;

    public constructor() { }
}

// Create a JsonObject generic class: Value

@JsonObject()
export class Value<R> {
    @JsonProperty() value: R;

    constructor(value: R) {
        this.value = value;
    }
}

// Create a JsonObject class: Item

@JsonObject()
export class Item {
    @JsonProperty({ name: 'name' })
    private readonly _name: string;

    @JsonProperty({ name: 'version' })
    private readonly _version: number;

    constructor(name: string, version: number) {
        this._name = name;
        this._version = version;
    }
}

// Create a JsonObject class that extends Society: Organization

@JsonObject()
export class Organization extends Society {
    @JsonProperty({ type: Zoo }) zoos: Array<Zoo>;
    @JsonProperty({ dataStructure: 'dictionary' })
    zoosName: { [id: string]: string };

    // To merge multiple properties in a single one
    // use the property `names`.
    // If you don't create your own merge with the `beforeDeserialize`
    // and `afterSerialize` function, it will just merge properties
    // in this one when using `deserialize` and split back
    // when using `serialize`
    @JsonProperty({
        name: [
            'mainShareholder',
            'secondaryShareholder',
            'thirdShareholder'
        ],
        type: Human,
        beforeDeserialize: value => Object.values(value),
        afterSerialize: value => {
            return {
                mainShareholder: value[0],
                secondaryShareholder: value[1],
                thirdShareholder: value[2]
            };
        }
    })
    shareholders: Array<Human>;
    miscellaneous: Value<Item>;
}


// Create a JsonObject class: Society

@JsonObject()
export class Society {
    // Here note the `required` option with the default value `'4'` 
    // it will not throw because the default value will be set instead of `undefined`
    @JsonProperty({ required: true }) id: string = '4';
    @JsonProperty() name: string;
}

Json data

// data.ts
export const data: any = {
    name: 'Zoos Organization',
    zoosName: {
        '15': 'The Greatest Zoo',
        '16': 'Zoo Zoo'
    },
    zoos: [
        {
            id: 15,
            name: 'The Greatest Zoo',
            city: 'Bordeaux',
            coordinates: [1, 2, 3],
            country: 'France',
            boss: {
                employeeId: 1,
                name: 'Bob Razowsky',
                birthDate: '1984-04-03T22:00:00.000Z',
                email: '[e-mail]',
                gender: 1,
                phoneNumber: '111-111-1111'
            },
            employees: [
                {
                    employeeId: 1,
                    name: 'Bob Razowsky',
                    birthDate: '1984-04-03T22:00:00.000Z',
                    email: '[e-mail]',
                    gender: 1,
                    phoneNumber: '111-111-1111'
                },
                {
                    employeeId: 2,
                    name: 'Mikasa Ackerman',
                    birthDate: '1984-01-11T22:00:00.000Z',
                    email: '[e-mail]',
                    gender: 0,
                    phoneNumber: '222-222-2222'
                },
                {
                    employeeId: 3,
                    name: 'Red Redington',
                    birthDate: '1970-12-04T22:00:00.000Z',
                    email: '[e-mail]',
                    gender: 1,
                    phoneNumber: '333-333-3333'
                },
                {
                    employeeId: 4,
                    name: 'Fried Richter',
                    birthDate: '1994-04-01T22:00:00.000Z',
                    email: '[e-mail]',
                    gender: 1
                }
            ],
            Animals: [
                {
                    id: 1,
                    name: 'Bagheera',
                    birthDate: '2010-01-11T22:00:00.000Z',
                    numberOfPaws: 4,
                    gender: 1,
                    childrenIdentifiers: [2, 3],
                    color: 'black',
                    isSpeckled: false,
                    status: 'Sick'
                },
                {
                    id: 2,
                    birthDate: '2017-03-10T22:00:00.000Z',
                    numberOfPaws: 4,
                    gender: 0,
                    color: 'blond',
                    isSpeckled: true,
                    status: 'Alive'
                },
                {
                    id: 3,
                    name: 'Ka',
                    birthDate: '2018-09-09T00:00:00.000Z',
                    numberOfPaws: 0,
                    gender: 1,
                    isPoisonous: true
                },
                {
                    id: 4,
                    name: 'Schrodinger',
                    numberOfPaws: 4,
                    gender: 1,
                    color: 'brown',
                    isSpeckled: false,
                    status: 'Dead and alive'
                }
            ],
            mascot: {
                id: 1,
                name: 'Bagheera',
                birthDate: '2010-01-11T22:00:00.000Z',
                numberOfPaws: 4,
                gender: 1,
                childrenIdentifiers: [2, 3],
                color: 'black',
                isSpeckled: false,
                status: 'Sick'
            },
            unknownAnimals: {
                '1': {
                    name: null
                }
            },
            phoneBook: {
                '1': [
                    { value: '111-111-1111' },
                    { value: '444-444-4444' }
                ],
                '2': [{ value: '222-222-2222' }],
                '3': ['333-333-3333']
            }
        },
        {
            id: 16,
            name: 'Zoo Zoo',
            city: 'Paris',
            coordinates: [4, 2, 3],
            country: 'France',
            boss: {
                employeeId: 2,
                name: 'Sully',
                birthDate: '1984-08-03T22:00:00.000Z',
                email: '[e-mail]',
                gender: 1,
                phoneNumber: {
                    countryCode: '33',
                    value: '0111111111'
                }
            },
            employees: [],
            Animals: [],
            mascot: null,
            unknownAnimals: {}
        }
    ],
    mainShareholder: {
        humanId: 100,
        name: 'Elon Musk',
        birthDate: '1971-06-28T22:00:00.000Z',
        gender: 1
    },
    secondaryShareholder: null,
    miscellaneous: {
        value: {
            name: 'Item A',
            version: 1
        }
    }
};

API

Decorators

@JsonObject()
Used to make a class serializable.

Parameters

options
Type: JsonObjectOptions
Optional: true
Description: The option to customize the serialization/deserialization of the target class.

Example

@JsonObject(options)
class MyClass {}

@JsonProperty()
Used to make a class property serializable, property will be ignored if not set.

Parameters

options
Type: string | JsonPropertyOptions
Optional: true
Description: The option to customize the serialization/deserialization of the target property.

Example

@JsonProperty(options) myProperty: string;

JsonSerializer

Constructor

constructor(options?: Partial<JsonSerializerOptions>) {}

Parameters

options
Type: Partial<JsonSerializerOptions>
Optional: true
Description: The options to customize the serializer.

Properties

options
Type: Partial<JsonSerializerOptions>
Optional: false
Description: The options to customize the serializer.

Default value:

{
    errorCallback: logError,
    nullishPolicy: {
        undefined: 'remove',
        null: 'allow'
    },
    additionalPropertiesPolicy: 'remove'
}

Methods

deserialize()
To use when you don't know if the value to deserialize is an object or an array.

deserialize<T extends object>(
    value: string | object | Array<object>,
    type: Type<T> | T
): T | Array<T|Nullish> | Nullish

Parameters

value
Type: string | object | Array<object>
Optional: false
Description: The value to deserialize.

type
Type: Type<T> | T
Optional: false
Description: The constructor class to deserialize into.

Return

T or Array<T|Nullish> or Nullish

---

deserializeObject()
To use when the value to deserialize is an object.

deserializeObject<T extends object>(
    obj: string | object,
    type: Type<T> | T
): T | Nullish

Parameters

obj
Type: string | object
Optional: false
Description: The object to deserialize.

type
Type: Type<T> | T
Optional: false
Description: The constructor class to deserialize into.

Return

T or Nullish

---

deserializeObjectArray()
To use when the value to deserialize is an array.

deserializeObjectArray<T extends object>(
    array: string | Array<any>,
    type: Type<T> | T
): Array<T|Nullish> | Nullish

Parameters

array
Type: string | Array<any>
Optional: false
Description: The object to deserialize.

type
Type: Type<T> | T
Optional: false
Description: The constructor class to deserialize into.

Return

Array<T|Nullish> or Nullish

---

serialize()
To use when you don't know if the value to serialize is an object or an array

serialize(value: object | Array<object>): object | Array<object|Nullish> | Nullish

Parameters

value
Type: object | Array<object>
Optional: false
Description: The object or the array of objects to serialize.

Return

object or Array<object|Nullish> or Nullish

---

serializeObject()
To use when the value to serialize is an object.

serializeObject(instance: object): object | Nullish

Parameters

instance
Type: object
Optional: false
Description: The object to serialize.

Return

object or Nullish

---

serializeObjectArray()
To use when the value to serialize is an array of objects.

serializeObjectArray(array: Array<object>): Array<object|Nullish> | Nullish

Parameters

array
Type: Array<object>
Optional: false
Description: The array of objects to serialize.

Return

Array<object|Nullish> or Nullish

Definitions

Types

JsonObjectOptions

constructorParams?: Array<unknown>;

JsonPropertyOptions

name?: string | Array<string>;
type?: Function | PredicateProto;
dataStructure?: DataStructure;
required?: boolean;
beforeSerialize?: IOProto;
afterSerialize?: IOProto;
beforeDeserialize?: IOProto;
afterDeserialize?: IOProto;

JsonSerializerOptions

errorCallback?: ErrorCallback = logError;
nullishPolicy: NullishPolicy = {
    undefined: 'remove',
    null: 'allow'
};
additionalPropertiesPolicy: Policy = 'remove';
formatPropertyName?: FormatPropertyNameProto;

NullishPolicy

undefined: Policy;
null: Policy;

Value types

DataStructure

'array' | 'dictionary' | 'map' | 'set'

Nullish

null | undefined

Policy

'allow' | 'disallow' | 'remove'

Function types

ErrorCallback

(message: string) => void

The library provide two built-in methods:

• logError that logs the error.
• throwError that throws the error.

FormatPropertyNameProto

(propertyName: string) => string;

IOProto

(property: any, currentInstance?: any) => any

PredicateProto

(property: any, parentProperty?: any) => any

Type<T>

new (...args: Array<any>) => T;

Note: represent a constructor.

Development

Prerequisites

• NodeJS: https://nodejs.org
• Yarn: https://yarnpkg.com

Install dependencies

yarn

Run build

yarn build

Run linter

yarn lint

Run tests

yarn test

Thanks to

Author

Gillian Pérard - @GillianPerard

Contributors

• Hyeonsoo David Lee - @civilizeddev