tiny-decoders

tiny-decoders

Type-safe data decoding for the minimalist, inspired by nvie/decoders and Elm’s JSON Decoders.

Supports TypeScript and Flow.

import {
  Decoder,
  array,
  boolean,
  either,
  fields,
  number,
  optional,
  string,
} from "tiny-decoders";

type User = {
  name: string;
  active: boolean;
  age: number | undefined;
  interests: Array<string>;
  id: string | number;
};

const userDecoder = fields(
  (field): User => ({
    name: field("full_name", string),
    active: field("is_active", boolean),
    age: field("age", optional(number)),
    interests: field("interests", array(string)),
    id: field("id", either(string, number)),
  })
);

const payload: unknown = getSomeJSON();

const user: User = userDecoder(payload);

/*
If we get here, `user` is now a valid `User`!
Otherwise, a `TypeError` is thrown.
The error can look like this:

    TypeError: object["age"]: (optional) Expected a number, but got: "30"
*/

️Full example

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➡️ Full readme

Changelog

Version 5.0.0 (2020-04-19)

• Changed: record is now called fields and now works with both objects and arrays. Besides being more flexible, this reduces the footprint of the library and means there’s one thing less to learn.
• Removed: tuple. Use fields instead.
• Changed: pair, tuple and array now work with any array-like objects, not just Arrays.
• Removed: mixedArray and mixedDict. Because of the above changes, mixedArray isn’t used internally anymore and mixedDict had to change to allow arrays. I haven’t really had a need for these outside tiny-decoders so I decided to remove them both.
• Added: The WithUndefinedAsOptional helper type for TypeScript. When inferring types from fields and autoRecord decoders, all fields are inferred as required, even ones where you use the optional decoder. The helper type lets you turn fields that can be undefined into optional fields, by changing all key: T | undefined to key?: T | undefined.