indexers

(⚠️ Experimental)

Parent: main.js|ts configuration

Type: (existingIndexers: Indexer[]) => Promise<Indexer[]>

Indexers are responsible for building Storybook's index of stories—the list of all stories and a subset of their metadata like id, title, tags, and more. The index can be read at the /index.json route of your Storybook.

The indexers API is an advanced feature that allows you to customize Storybook's indexers, which dictate how Storybook indexes and parses files into story entries. This adds more flexibility to how you can write stories, including which language stories are defined in or where to get stories from.

They are defined as a function that returns the full list of indexers, including the existing ones. This allows you to add your own indexer to the list, or to replace an existing one:

// Replace your-framework with the framework you are using (e.g., react-webpack5, vue3-vite)
import type { StorybookConfig } from '@storybook/your-framework';
 
const config: StorybookConfig = {
  framework: '@storybook/your-framework',
  stories: [
    '../src/**/*.mdx',
    '../src/**/*.stories.@(js|jsx|mjs|ts|tsx)',
    // 👇 Make sure files to index are included in `stories`
    '../src/**/*.custom-stories.@(js|jsx|ts|tsx)',
  ],
  experimental_indexers: async (existingIndexers) => {
    const customIndexer = {
      test: /\.custom-stories\.[tj]sx?$/,
      createIndex: // See API and examples below...
    };
    return [...existingIndexers, customIndexer];
  },
};
 
export default config

Unless your indexer is doing something relatively trivial (e.g. indexing stories with a different naming convention), in addition to indexing the file, you will likely need to transpile it to CSF so that Storybook can read them in the browser.

Indexer

Type:

{
  test: RegExp;
  createIndex: (fileName: string, options: IndexerOptions) => Promise<IndexInput[]>;
}

Specifies which files to index and how to index them as stories.

test

(Required)

Type: RegExp

A regular expression run against file names included in the stories configuration that should match all files to be handled by this indexer.

createIndex

(Required)

Type: (fileName: string, options: IndexerOptions) => Promise<IndexInput[]>

Function that accepts a single CSF file and returns a list of entries to index.

fileName

Type: string

The name of the CSF file used to create entries to index.

IndexerOptions

Type:

{
  makeTitle: (userTitle?: string) => string;
}

Options for indexing the file.

makeTitle

Type: (userTitle?: string) => string

A function that takes a user-provided title and returns a formatted title for the index entry, which is used in the sidebar. If no user title is provided, one is automatically generated based on the file name and path.

See IndexInput.title for example usage.

IndexInput

Type:

{
  exportName: string;
  importPath: string;
  type: 'story';
  metaId?: string;
  name?: string;
  tags?: string[];
  title?: string;
  __id?: string;
}

An object representing a story to be added to the stories index.

exportName

(Required)

Type: string

For each IndexInput, the indexer will add this export (from the file found at importPath) as an entry in the index.

importPath

(Required)

Type: string

The file to import from, e.g. the CSF file.

It is likely that the fileName being indexed is not CSF, in which you will need to transpile it to CSF so that Storybook can read it in the browser.

type

(Required)

Type: 'story'

The type of entry.

metaId

Type: string

Default: Auto-generated from title

Define the custom id for meta of the entry.

If specified, the export default (meta) in the CSF file must have a corresponding id property, to be correctly matched.

name

Type: string

Default: Auto-generated from exportName

The name of the entry.

tags

Type: string[]

Tags for filtering entries in Storybook and its tools.

title

Type: string

Default: Auto-generated from default export of importPath

Determines the location of the entry in the sidebar.

Most of the time, you should not specify a title, so that your indexer will use the default naming behavior. When specifying a title, you must use the makeTitle function provided in IndexerOptions to also use this behavior. For example, here's an indexer that merely appends a "Custom" prefix to the title derived from the file name:

// Replace your-framework with the framework you are using (e.g., react-webpack5, vue3-vite)
import type { StorybookConfig } from '@storybook/your-framework';
import type { Indexer } from '@storybook/types';
 
const combosIndexer: Indexer = {
  test: /\.stories\.[tj]sx?$/,
  createIndex: async (fileName, { makeTitle }) => {
    // 👇 Grab title from fileName
    const title = fileName.match(/\/(.*)\.stories/)[1];
 
    // Read file and generate entries ...
 
    return entries.map((entry) => ({
      type: 'story',
      // 👇 Use makeTitle to format the title
      title: `${makeTitle(title)} Custom`,
      importPath: fileName,
      exportName: entry.name,
    }));
  },
};
 
const config: StorybookConfig = {
  framework: '@storybook/your-framework',
  stories: ['../src/**/*.mdx', '../src/**/*.stories.@(js|jsx|ts|tsx)'],
  experimental_indexers: async (existingIndexers) => [...existingIndexers, combosIndexer];
};
 
export default config;

__id

Type: string

Default: Auto-generated from title/metaId and exportName

Define the custom id for the story of the entry.

If specified, the story in the CSF file must have a corresponding __id property, to be correctly matched.

Only use this if you need to override the auto-generated id.

Transpiling to CSF

The value of importPath in an IndexInput must resolve to a CSF file. Most custom indexers, however, are only necessary because the input is not CSF. Therefore, you will likely need to transpile the input to CSF, so that Storybook can read it in the browser and render your stories.

Transpiling the custom source format to CSF is beyond the scope of this documentation. This transpilation is often done at the builder level (Vite and/or Webpack), and we recommend using unplugin to create plugins for multiple builders.

The general architecture looks something like this:

1. Using the stories configuration, Storybook finds all files that match the test property of your indexer
2. Storybook passes each matching file to your indexer's createIndex function, which uses the file contents to generate and return a list of index entries (stories) to add to the index
3. The index populates the sidebar in the Storybook UI

1. In the Storybook UI, the user navigates to a URL matching the story id and the browser requests the CSF file specified by the importPath property of the index entry
2. Back on the server, your builder plugin transpiles the source file to CSF, and serves it to the client
3. The Storybook UI reads the CSF file, imports the story specified by exportName, and renders it

Let's look at an example of how this might work.

First, here's an example of a non-CSF source file:

// Button.variants.js|ts
 
import { variantsFromComponent, createStoryFromVariant } from '../utils';
import { Button } from './Button';
 
/**
 * Returns raw strings representing stories via component props, eg.
 * 'export const PrimaryVariant = {
 *    args: {
 *      primary: true
 *    },
 *  };'
 */
export const generateStories = () => {
  const variants = variantsFromComponent(Button);
  return variants.map((variant) => createStoryFromVariant(variant));
};

The builder plugin would then:

1. Receive and read the source file
2. Import the exported generateStories function
3. Run the function to generate the stories
4. Write the stories to a CSF file

That resulting CSF file would then be indexed by Storybook. It would look something like this:

// virtual:Button.variants.js|ts
 
import { Button } from './Button';
 
export default {
  component: Button,
};
 
export const Primary = {
  args: {
    primary: true,
  },
};

Examples

Some example usages of custom indexers include:

// Replace your-framework with the framework you are using (e.g., react-webpack5, vue3-vite)
import type { StorybookConfig } from '@storybook/your-framework';
import type { Indexer } from '@storybook/types';
 
import fs from 'fs/promises';
 
const jsonStoriesIndexer: Indexer = {
  test: /stories\.json$/,
  createIndex: async (fileName) => {
    const content = JSON.parse(fs.readFileSync(fileName));
 
    const stories = generateStoryIndexesFromJson(content);
 
    return stories.map((story) => {
      type: 'story',
      importPath: `virtual:jsonstories--${fileName}--${story.componentName}`,
      exportName: story.name
    });
  },
};
 
const config: StorybookConfig = {
  framework: '@storybook/your-framework',
  stories: [
    '../src/**/*.mdx',
    '../src/**/*.stories.@(js|jsx|mjs|ts|tsx)',
    // 👇 Make sure files to index are included in `stories`
    '../src/**/*.stories.json',
  ],
  experimental_indexers: async (existingIndexers) => [...existingIndexers, jsonStoriesIndexer];
};
 
export default config;

{
  "Button": {
    "componentPath": "./button/Button.jsx",
    "stories": {
      "Primary": {
        "args": {
          "primary": true
        },
      "Secondary": {
        "args": {
          "primary": false
        }
      }
    }
  },
  "Dialog": {
    "componentPath": "./dialog/Dialog.jsx",
    "stories": {
      "Closed": {},
      "Open": {
        "args": {
          "isOpen": true
        }
      },
    }
  }
}

// vite-plugin-storybook-json-stories.ts
 
import type { PluginOption } from 'vite';
import fs from 'fs/promises';
 
function JsonStoriesPlugin(): PluginOption {
  return {
    name: 'vite-plugin-storybook-json-stories',
    load(id) {
      if (!id.startsWith('virtual:jsonstories')) {
        return;
      }
 
      const [, fileName, componentName] = id.split('--');
      const content = JSON.parse(fs.readFileSync(fileName));
 
      const { componentPath, stories } = getComponentStoriesFromJson(content, componentName);
 
      return `
        import ${componentName} from '${componentPath}';
 
        export default { component: ${componentName} };
 
        ${stories.map((story) => `export const ${story.name} = ${story.config};\n`)}
      `;
    },
  };
}