How to write stories

A story captures the rendered state of a UI component. Given a set of arguments, it can be a simple object with annotations or a component that describes its behavior and appearance.

A story captures the rendered state of a UI component. It's an object with annotations that describe the component's behavior and appearance given a set of arguments.

Storybook uses the generic term arguments (args for short) when talking about React’s props, Vue’s props, Angular’s @Input, and other similar concepts.

Where to put stories

A component’s stories are defined in a story file that lives alongside the component file. The story file is for development-only, and it won't be included in your production bundle. In your filesystem, it looks something like this:

components/
├─ Button/
│  ├─ Button.js | ts | jsx | tsx | vue | svelte
│  ├─ Button.stories.js | ts | jsx | tsx | svelte

Component Story Format

We can define stories according to the Component Story Format (CSF), an ES6 module-based standard that is easy to write and portable between tools, or rely on the community-led project Svelte CSF which provides a similar experience.

With Svelte CSF, the essential elements are the defineMeta function, which describes the component, and the Story component, which describes the stories. This pattern is different from the standard CSF, which uses a default export and named exports to apply the same concepts.

We define stories according to the Component Story Format (CSF), an ES6 module-based standard that is easy to write and portable between tools.

The key ingredients are the meta (or default export) that describes the component, and named exports that describe the stories.

Default export

The defineMeta function in Svelte CSF with native templating syntax controls how Storybook lists your stories and provides information used by addons. However, if you're not using this story format and relying on standard CSF, use the default export to achieve the same result. Below is an example of a story file with both approaches:

The default export metadata controls how Storybook lists your stories and provides information used by addons. For example, here’s the meta (or default export) for a story file Button.stories.js|ts:

Starting with Storybook version 7.0, story titles are analyzed statically as part of the build process. The *default* export must contain a `title` property that can be read statically or a `component` property from which an automatic title can be computed. Using the `id` property to customize your story URL must also be statically readable.

Defining stories

If you're using Svelte CSF, define your stories with the Story component, otherwise use the named exports of a standard CSF file. We recommend you use UpperCamelCase for your story exports. Here’s how to render Button in the “primary” state and export a story called Primary using both methods.

Use the named exports of a CSF file to define your component’s stories. We recommend you use UpperCamelCase for your story exports. Here’s how to render Button in the “primary” state and export a story called Primary.

Unlike regular CSF, when using Svelte CSF, you cannot use args for children. Instead, you pass children in-between the opening and closing Story tags and it will be passed to the component as the children snippet prop.

<script module>
  import { defineMeta } from '@storybook/addon-svelte-csf';
 
  import Alert from './Alert.svelte';
 
  const { Story } = defineMeta({
    component: Alert,
  });
</script>
<Story name="Alert with children">
  Alert text
</Story>

If you want to render the children as the entire story itself, you can use the asChild prop of the Story component, which will ignore the default component rendering and render the children directly.

<Story
  name="Default Button in alert"
  asChild
/>
  <Alert>
    Alert text
    <Button />
  </Alert>
</Story>

Note that features which require args, like Controls, will not work when using asChild. You can customize the rendering of a story and retain the ability to use args by using a custom render function.

Custom rendering

By default, stories will render the component defined in the defineMeta call (for Svelte CSF) or in the default export (for CSF), with the args passed to it.

If you need to customize the rendering of your story, you can provide a snippet (for Svelte CSF) or a render function (for CSF) that accepts args and renders whatever you need.

For example, if you want to render a Button inside an Alert:

<Story
  name="Primary in alert"
  args={{
    label: 'Button',
    primary: true,
  }}>
  {#snippet template(args)}
    <Alert>
      Alert text
      <Button {...args} />
    </Alert>
  {/snippet}
</Story>

Note how the template snippet or render function spreads args onto the Button component. This ensures that features like Controls will work as expected, allowing you to dynamically change the Button's properties in the Storybook UI.

You can re-use the same render function across stories by applying it at the meta level. For Svelte CSF, this can be done by defining the template snippet outside of the story and assigning it to the render property of the defineMeta function. For CSF, you can define a render function in the meta (or default export).

<script module>
  import { defineMeta } from '@storybook/addon-svelte-csf';
  import Button from './Button.svelte';

  const { Story } = defineMeta({
    component: Button,
    render: template,
  });
</script>

{#snippet template(args)}
  <Alert>
    Alert text
    <Button {...args} />
  </Alert>
{/snippet}

<Story name="Default in alert" args={{ label: 'Button' }} />

<Story name="Primary in alert" args={{ label: 'Button', primary: true }} />

Whatever you define at the meta level can be overridden at the story level, so you can still customize the rendering of individual stories if needed.

Finally, render functions and template snippets receive a second context argument, which contains all other details for the story, including parameters, globals, and more.

By default, stories will render the component defined in the meta (or default export), with the args passed to it. If you need to render something else, you can provide a function to the render property that returns the desired output.

For example, if you want to render a Button inside an Alert, you can define a custom render function like this:

Note how the render function spreads args onto the Button component. This ensures that features like Controls will work as expected, allowing you to dynamically change the Button's properties in the Storybook UI.

You can re-use the same render function across stories by applying it at the meta level:

Whatever you define at the meta level can be overridden at the story level, so you can still customize the rendering of individual stories if needed.

Finally, render functions receive a second context argument, which contains all other details for the story, including parameters, globals, and more.

React Hooks are convenient helper methods to create components using a more streamlined approach. You can use them while creating your component's stories if you need them, although you should treat them as an advanced use case. We recommend args as much as possible when writing your own stories. As an example, here’s a story that uses React Hooks to change the button's state:

Solid Signals are convenient helper methods to create components using a more streamlined approach. You can use them while creating your component's stories if you need them, although you should treat them as an advanced use case. We recommend args as much as possible when writing your own stories. As an example, here’s a story that uses Solid Signals to change the button's state:

Rename stories

By default, Storybook uses the name of the story export as the basis for the story name. However, you can customize the name of your story by adding a name property to the story object. This is useful when you want to provide a more descriptive or user-friendly name for your story.

If you're using Svelte CSF, the name property is usually fairly descriptive and user-friendly already, so there is little need for renaming. However, the name is used as the basis for the export name, which must be unique within a file. In rare cases, this can lead to naming conflicts. For example, stories with the names "Primary" and "Primary!" would both be transformed to the "Primary" export name. To avoid this, you can use the exportName property to specify a unique export name for your story. exportName is also helpful to provide a more useful named export when re-using stories, e.g. as portable stories.

Your story will now be shown in the sidebar with the given text.

How to write stories

With Svelte, stories can be defined as objects using standard CSF or with Svelte CSF's Story component. Both methods describe how to render a component. You can have multiple stories per component, and those stories can build upon one another. For example, we can add Secondary and Tertiary stories based on our Primary story above.

A story is an object that describes how to render a component. You can have multiple stories per component, and those stories can build upon one another. For example, we can add Secondary and Tertiary stories based on our Primary story from above.

What’s more, you can import args to reuse when writing stories for other components, and it's helpful when you’re building composite components. For example, if we make a ButtonGroup story, we might remix two stories from its child component Button.

When Button’s signature changes, you only need to change Button’s stories to reflect the new schema, and ButtonGroup’s stories will automatically be updated. This pattern allows you to reuse your data definitions across the component hierarchy, making your stories more maintainable.

That’s not all! Each of the args from the story function are live editable using Storybook’s Controls panel. It means your team can dynamically change components in Storybook to stress test and find edge cases.

You can also use the Controls panel to edit or save a new story after adjusting its control values.

This feature is not supported with the Svelte CSF. To opt-in to this feature with Svelte, you must use Storybook's [Component Story Format](../api/csf/index.mdx).

Addons can enhance args. For instance, Actions auto-detects which args are callbacks and appends a logging function to them. That way, interactions (like clicks) get logged in the actions panel.

Using the play function

Storybook's play function is a convenient helper methods to test component scenarios that otherwise require user intervention. They're small code snippets that execute once your story renders. For example, suppose you wanted to validate a form component, you could write the following story using the play function to check how the component responds when filling in the inputs with information:

You can interact with and debug your story's play function in the interactions panel.

Using parameters

Parameters are Storybook’s method of defining static metadata for stories. A story’s parameters can be used to provide configuration to various addons at the level of a story or group of stories.

For instance, suppose you wanted to test your Button component against a different set of backgrounds than the other components in your app. You might add a component-level backgrounds parameter:

This parameter would instruct the backgrounds feature to reconfigure itself whenever a Button story is selected. Most features and addons are configured via a parameter-based API and can be influenced at a global, component, and story level.

Using decorators

Decorators are a mechanism to wrap a component in arbitrary markup when rendering a story. Components are often created with assumptions about ‘where’ they render. Your styles might expect a theme or layout wrapper, or your UI might expect specific context or data providers.

A simple example is adding padding to a component’s stories. With Svelte, you can either use an auxiliary component to wrap your stories with the required spacing or layout elements, or ignore the concept of decorators entirely and define them inline in a template.

{ /* prettier-ignore-start */}

{ /* prettier-ignore-end */}

A simple example is adding padding to a component’s stories. Accomplish this using a decorator that wraps the stories in a div with padding, like so:

Decorators can be more complex and are often provided by addons. You can also configure decorators at the story, component and global level.

Stories for two or more components

Sometimes you may have two or more components created to work together. For instance, if you have a parent List component, it may require child ListItem components.

In such cases, it makes sense to customize the rendering to output the List component with different numbers of ListItem children.

You can also reuse story data from the child ListItem in your List component. That’s easier to maintain because you don’t have to update it in multiple places.