W3C Design Tokens Parser

This package provides a TypeScript implementation of the parser for the W3C Design Tokens Format Module specification. It also includes several methods to work with the tokens and their values.

Installation

Using npm

$ npm install @nclsndr/w3c-design-tokens-parser

Using yarn

$ yarn add @nclsndr/w3c-design-tokens-parser

Using pnpm

$ pnpm add @nclsndr/w3c-design-tokens-parser

Usage

Parse an initial token tree

We start from a JSON parsed JavaScript object that represents a design token tree.

import { parseDesignTokens } from '@nclsndr/w3c-design-tokens-parser';

const tokens = {
  color: {
    $type: 'color',
    blue: {
      100: {
        $value: '#0d3181',
      },
    },
  },
};

const tokenTree = parseDesignTokens();

The TokenTree exposes various methods to either get the parse errors, the tokens, or work with the values of the tokens.

// Get errors
tokenTree.getErrors();

// Get a given token
tokenTree.getToken(['color', 'blue', 100]);
// with a type guard to help out the TS compiler
tokenTree.getTokenOfType('color', ['color', 'blue', 100]);

// Get tokens
tokenTree.getAllTokens();
tokenTree.getAllTokensByType('color');
// With a callback style
tokenTree.mapTokensByType('color', (token) => {
  // ...
});

// Get groups
tokenTree.getAllGroups();
tokenTree.getGroup(['color']);

Once we grabbed some tokens, we can use the Token methods to move further.

The most basic operation is to get the JSON value of a token. Let's take the following:

const tokens: JSONTokenTree = {
  color: {
    $type: 'color',
    blue: {
      $value: '#0000FF',
    },
    accent: {
      $value: '{color.blue}',
    },
    borderActive: {
      $value: '{color.accent}',
    },
  },
  border: {
    $type: 'border',
    active: {
      $value: {
        width: '1px',
        style: 'solid',
        color: '{color.borderActive}',
      },
    },
  },
};
const tokenTree = parseDesignTokens(tokens);

const fullyResolvedColorValues = tokenTree.mapTokensByType('color', (token) => {
  console.log(token.summary);

  return token.getJSONValue({
    resolveToDepth: Infinity,
    // resolveToDepth allows to resolve the token value to a certain depth.
    // resolveToDepth: -1 is equivalent to resolveToDepth: Infinity
  });
});
console.log(fullyResolvedColorValues); // [ '#0000FF', '#0000FF', '#0000FF' ]

const partiallyResolvedColorValues = tokenTree.mapTokensByType(
  'color',
  (token) => {
    return token.getJSONValue({
      resolveToDepth: 1, // resolving aliases up to 1 level
    });
  },
);
console.log(partiallyResolvedColorValues); // [ '#0000FF', '#0000FF', '{color.blue}' ]

Whenever we want to work with the value of a token, we need to consider all the potential forms the value might take. The token .getValueMapper() method provides an API to generalize the approach to the token values where most of them can be aliased at any point in the tree.

With a color, we might have a raw value or an alias reference.

const colorValues = tokenTree.mapTokensByType('color', (colorToken) => {
  return colorToken
    .getValueMapper()
    .mapScalarValue((scalarValue) => scalarValue.raw)
    .mapAliasReference(
      (aliasReference) =>
        `var(--${aliasReference.to.treePath.array.join('-')})`,
    )
    .unwrap();
});
console.log(colorValues); // [ '#0000FF', 'var(--color-blue)', 'var(--color-accent)' ]

With a border, we might have an alias reference or an object, which might contain an alias reference for each of its properties.

const borderValues = tokenTree.mapTokensByType('border', (token) => {
  return token
    .getValueMapper()
    .mapAliasReference((ref) => `var(--${ref.to.treePath.join('-')})`)
    .mapObjectValue((obj) =>
      obj.flatMap((value) => {
        const width = value.width
          .mapAliasReference((ref) => `var(--${ref.to.treePath.join('-')}`)
          .mapScalarValue((value) => value.raw)
          .unwrap();
        const style = value.style
          .mapAliasReference((ref) => `var(--${ref.to.treePath.join('-')}`)
          .mapScalarValue((value) => value.raw)
          .unwrap();
        const color = value.color
          .mapAliasReference((ref) => `var(--${ref.to.treePath.join('-')}`)
          .mapScalarValue((value) => value.raw)
          .unwrap();

        return [width, style, color].join(' ');
      }),
    )
    .unwrap();
});

console.log(borderValues); // [ '1px solid var(--color-borderActive' ]

In order to cut down the complexity of aliases one would have to resolve, the token .getValueMapper() methods takes a resolveAtDepth option, which can bring back the raw value of the token at a certain depth, as far as the referenced token exists.

const cssColorTokens = tokenTree.mapTokensByType('color', (colorToken) => {
  return {
    key: colorToken.name,
    value: colorToken
      .getValueMapper({
        resolveAtDepth: Infinity,
      })
      .mapScalarValue((scalarValue) => scalarValue.raw)
      .mapAliasReference(
        (aliasReference) =>
          `var(--${aliasReference.to.treePath.array.join('-')})`,
      )
      .unwrap(),
  };
});

API

• TokenTree
  • Token
    • ValueMapper
      • ScalarValue
      • AliasReference
      • ObjectValue
      • ArrayValue