Design Tokens Format Module

— A TypeScript implementation of the Design Tokens Format Module specification along with some utility functions

Abstract

This packages aims to provide the most agnostic JavaScript/TypeScript definitions from the Design Tokens Format Module specification, for library developers and tooling creators.

Join the conversation on the W3C Design Tokens Community Group repository.

⚠️ Please note, the DTCG specification is NOT stable yet, breaking changes might occur in the future.

Installation

Using npm

npm install design-tokens-format-module

Using yarn

yarn add design-tokens-format-module

Using pnpm

pnpm add design-tokens-format-module

Usage

This module provides all the type definitions and the most basic helpers required to work with a JSON design token tree.

Token tree

Constrain a JSON object that represents a design token tree.

import { JSONTokenTree } from 'design-tokens-format-module';

const tokenTree = {
  color: {
    primary: {
      $type: 'color',
      $value: '#000000',
    },
  },
  spacing: {
    small: {
      $type: 'dimension',
      $value: '8px',
    },
  },
} satisfies JSONTokenTree;

Design Token

Each design token type is available as a TypeScript namespace.

import {
  Color // Dimension, FontFamily... 
} from 'design-tokens-format-module';

declare function parseColorToken(token: unknown): Color.Token;
declare function parseColorValue(tokens: unknown): Color.Value;
declare function matchIsColorTokenTypeName(
  name: string,
): name is Color.TypeName;

Design token type names

All token type names are available as a constant.

import { tokenTypeNames } from 'design-tokens-format-module';

for(const tokenTypeName of tokenTypeNames) {
  // color, dimension...
}

All token types

All token type signatures are available within a type union.

import { DesignToken } from 'design-tokens-format-module';

declare function parseDesignToken(token: unknown): DesignToken;

Matchers

JSON values can be evaluated against the token signature

import { matchIsToken, matchIsTokenTypeName, matchIsAliasValue } from 'design-tokens-format-module';

function validateToken(token: unknown) {
  if (matchIsToken(token)) {
    const isValidType = matchIsTokenTypeName(token.$type ?? '');
    if(matchIsAliasValue(token.$value)) {
      // ...
    }
  }
  // ...
}

Alias utils

Alias values can be validated and parsed.

import { captureAliasPath } from 'design-tokens-format-module';

const result = captureAliasPath('{path.to.token}');

if(result.status === 'ok') {
  result.value // string[]
} else {
  switch (result.error.tag) {
    case 'TYPE_ERROR': {
      result.error.message // Expected a string value. Got [x].
      break;
    }
    case 'FORMAT_ERROR': {
      result.error.message // Expected an alias value. Got [x].
      break;
    }
  }
}

Enum-like constants

Some token types have a fixed set of values. These are available as constants.

import { fontWeightValues, strokeStyleStringValues, strokeStyleLineCapValues } from 'design-tokens-format-module';

Previous versions

The packages goal has shifted from being a generic parser — which requires way more feedback — to a reliable source of truth for the DTCG implementations in the JavaScript land.

The features and APIs available before version 0.9.0 has been relocated to a new location where they get revamped and improved.

Contributing

If you find any typos, errors, or additional improvements, feel free to contribute to the project.

Development

Install dependencies.

npm install

Run test in watch mode.

npm run test

Please add tests to cover the new functionality or bug fix you are working upon.

Before opening a PR

We expect the tests and the build to pass for a PR to be reviewed and merged.

npm run test --run

npm run build

API

AliasValue (type)

type AliasValue = `{${string}}`;

Json (namespace)

namespace Json {
  export type Value = JSONValue;
  export type Object = JSONObject;
  export type Array = JSONArray;
  export type Primitive = string | number | boolean | null;
}

JSONTokenTree (type)

type JSONTokenTree = {
  [key: string]: DesignToken | JSONTokenTree | GroupProperties;
} & GroupProperties;

Color,Dimension, ... (namespace)

namespace TokenTypeName {
  export type TypeName = TypeName;
  export type Value = Value;
  export type Token = Token;
}

DesignToken (type)

type DesignToken =
  | ColorToken
  | DimensionToken
  // | ...

TokenTypeName (type)

type TokenTypeName = 
  | 'color'
  | 'dimension'
  // | ... 

captureAliasPath (function)

const CAPTURE_ALIAS_PATH_ERRORS = {
  TYPE_ERROR: 'Expected a string value.',
  // ...
} as const;

type ValidationError = {
  [k in keyof Writable<typeof CAPTURE_ALIAS_PATH_ERRORS>]?: {
    message: string;
  };
};

type Result<T, E> =
  | {
  status: 'ok';
  value: T;
  error?: undefined;
}
  | {
  status: 'error';
  error: E;
  value?: undefined;
};

declare function captureAliasPath(
  value: unknown,
): Result<Array<string>, ValidationError>;
declare function captureAliasPath<AsString extends boolean | undefined>(
  value: unknown,
  asString: AsString,
): Result<AsString extends true ? string : Array<string>, ValidationError>;

Usage

const result = captureAliasPath('{path.to.token}');

if(result.status === 'ok') {
  result.value // string[]
} else {
  switch (result.error.tag) {
    case 'TYPE_ERROR': {
      result.error.message // Expected a string value. Got [x].
      break;
    }
    case 'FORMAT_ERROR': {
      result.error.message // Expected an alias value. Got [x].
      break;
    }
  }
}

matchIsAliasValue (function)

declare function matchIsAliasValue(candidate: unknown): candidate is AliasValue;

matchIsGroup (function)

declare function matchIsGroup(candidate: unknown): candidate is JSONTokenTree;

matchIsToken (function)

declare function matchIsToken(candidate: unknown): candidate is DesignToken;

matchIsTokenTypeName (function)

declare function matchIsTokenTypeName(candidate: unknown): candidate is TokenTypeName;

ALIAS_PATH_SEPARATOR (constant)

const ALIAS_PATH_SEPARATOR = '.';

tokenTypeNames (constant)

const tokenTypeNames = [
  'color',
  'dimension',
  // ...
] as const;

fontWeightValues (constant)

const fontWeightValues = [
  100,
  'thin',
  'hairline',
  // ...
] as const;

strokeStyleStringValues (constant)

const strokeStyleStringValues = [
  'solid',
  'dashed',
  // ...
] as const;

strokeStyleLineCapValues (constant)

const strokeStyleLineCapValues = [
  'round',
  'butt',
  // ...
] as const;