Serializing/Deserializing JSON to TypeScript with conversions

Question

I am trying to serialize TypeScript objects to JSON and vice-versa. While converting, certain fields have to be transformed, e.g. Date objects to ISO 8601 strings, enumerations to values required by the wire format, etc. I am currently creating type definitions for both the TypeScript object and the JSON object (trying to avoid typing the JSON object as any). Is there a better pattern for doing this?

Example

TypeScript object:

{
  name: 'John Smith',
  title: 'Sr. Developer',
  dob: new Date('1990-05-01T09:00:00Z');
}

JSON object:

{
  "name": "John Smith",
  "title": "Sr. Developer",
  "dob": "1990-05-01T09:00:00Z";
}

Here's the code to serialize/deserialize + the type definitions for the two formats:

interface Person {
    name: string;
    title: string;
    dob: Date;
}

interface JsonPerson {
    name: string;
    title: string;
    dob: string; // ISO 8601 format
}

function serialize(person: Person): JsonPerson {
    const { dob, ...rest } = person;
    return {
        dob: dob.toISOString(),
        ...rest
    }
}

function deserialize(jsonPerson: JsonPerson): Person {
    const { dob, ...rest } = jsonPerson;
    return {
        dob: new Date(dob),
        ...rest
    }
}

I would think you'd only need the deserialization code, since serialization should just be JSON.stringify(Person)... — Heretic Monkey
– Heretic Monkey, Commented May 14, 2020 at 0:00

basarat · Accepted Answer · 2020-05-14 00:28:05Z

2

The default Date.prototype.toJSON already uses the ISO string so you don't need to do dob.toISOString()

What you have is fine and generally what I prefer as well (explicit serialization / deserialization). I also have a video on the subject.

But if you want to use a serialization library here are two that I recommend for TypeScript that use decorators:

Part of the mobx ecosystem (which is another thing I love) https://github.com/mobxjs/serializr
A less popular but equally impressive library : https://github.com/danrevah/typeserializer

answered May 14, 2020 at 0:28

basarat

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3 Comments

Naresh Over a year ago

Thanks for the confirmation, Basarat, and nice video on this subject! BTW, I am also a fan of MobX and in fact have have written a router based on it: nareshbhatia.github.io/mobx-state-router

Naresh Over a year ago

Just confirming, while automatic serialization of dates works, automatic deserialization of strings to dates will not happen, correct? I will need the new Date(dob) during deserialization.

basarat Over a year ago

` automatic deserialization of strings to dates will not happen, correct? I will need the new Date(dob) during deserialization` Correct 🌹

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