(⚠️ Experimental)
While this feature is experimental, it must be specified by the experimental_indexers property of StorybookConfig.
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:
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:
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:
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:
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:
__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:
- Using the
storiesconfiguration, Storybook finds all files that match thetestproperty of your indexer - Storybook passes each matching file to your indexer's
createIndexfunction, which uses the file contents to generate and return a list of index entries (stories) to add to the index - The index populates the sidebar in the Storybook UI
- In the Storybook UI, the user navigates to a URL matching the story id and the browser requests the CSF file specified by the
importPathproperty of the index entry - Back on the server, your builder plugin transpiles the source file to CSF, and serves it to the client
- 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:
The builder plugin would then:
- Receive and read the source file
- Import the exported
generateStoriesfunction - Run the function to generate the stories
- Write the stories to a CSF file
That resulting CSF file would then be indexed by Storybook. It would look something like this:
Examples
Some example usages of custom indexers include:
Generating stories dynamically from fixture data or API endpoints
This indexer generates stories for components based on JSON fixture data. It looks for *.stories.json files in the project, adds them to the index and separately converts their content to CSF.
An example input JSON file could look like this:
A builder plugin will then need to transform the JSON file into a regular CSF file. This transformation could be done with a Vite plugin similar to this:
Generating stories with an alternative API
You can use a custom indexer and builder plugin to create your API to define stories extending the CSF format. To learn more, see the following proof of concept to set up a custom indexer to generate stories dynamically. It contains everything needed to support such a feature, including the indexer, a Vite plugin, and a Webpack loader.
Defining stories in non-JavaScript language
Custom indexers can be used for an advanced purpose: defining stories in any language, including template languages, and converting the files to CSF. To see examples of this in action, you can refer to @storybook/addon-svelte-csf for Svelte template syntax and storybook-vue-addon for Vue template syntax.
