Serializing Promises

Serializing promises or values containing primises.

stringifyAsync

The easiest way to serialize a promise with seria is using seria.stringifyAsync.

import { stringifyAsync } from "seria";

const delay = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));

const hero = {
  name: Promise.resolve("Shoto Todoroki"),
  quirk: Promise.resolve("Half-Cold Half-Hot"),
  age: Promise.resolve(16),
  heroName: delay(1000).then(() => Symbol.for("Shoto")),
};

const json = seria.stringifyAsync(hero);

For most cases this is enough, stringifyAsync will await all the promises found before returning the serialized value that then can be parsed back with seria.parse, all the promises returned by parse with be promises which value is just a Promise.resolve(value).

But when you are communicating between a server and client maybe you don't want your client to wait for all the promises to resolve to get the value back, for those use cases you need to use seria.stringifyToStream and seria.parseFromStream.

stringifyToStream

seria.stringifyToStream as the name says, takes a value and returns a ReadableStream which stream each value and resolved Promise value.

import { stringifyToStream } from "seria";

const hero = {
  name: Promise.resolve("Yu Takeyama"),
  quirk: Promise.resolve("Gigantification"),
  age: Promise.resolve(24),
  heroName: delay(1000).then(() => Symbol.for("Mt. Lady")),
};

const stream = stringifyToStream(hero);

The returting stream will stream the values, first the values name, quirk and age and after 1000ms the value heroName, to retrieve the original value back you need to use seria.parseFromStream.

parseFromStream

seria.parseFromStream as the name suggest takes a stream and deserializes it to a single value.

import { parseFromStream } from "seria";

const stream = getStream();
const value = await parseFromStream(stream);