Decorators

A decorator is a way to wrap a story in extra “rendering” functionality. Many addons define decorators to augment your stories with extra rendering or gather details about how your story renders.

When writing stories, decorators are typically used to wrap stories with extra markup or context mocking.

Wrap stories with extra markup

Some components require a “harness” to render in a useful way. For instance, if a component runs right up to its edges, you might want to space it inside Storybook. Use a decorator to add spacing for all stories of the component.

import { YourComponent } from './YourComponent';
 
export default {
  component: YourComponent,
  decorators: [
    (Story) => (
      <div style={{ margin: '3em' }}>
        {/* 👇 Decorators in Storybook also accept a function. Replace <Story/> with Story() to enable it  */}
        <Story />
      </div>
    ),
  ],
};

“Context” for mocking

The second argument to a decorator function is the story context which contains the properties:

• args - the story arguments. You can use some args in your decorators and drop them in the story implementation itself.
• argTypes- Storybook's argTypes allow you to customize and fine-tune your stories args.
• globals - Storybook-wide globals. In particular you can use the toolbars feature to allow you to change these values using Storybook’s UI.
• hooks - Storybook's API hooks (e.g., useArgs).
• parameters- the story's static metadata, most commonly used to control Storybook's behavior of features and addons.
• viewMode- Storybook's current active window (e.g., canvas, docs).

This context can be used to adjust the behavior of your decorator based on the story's arguments or other metadata. For example, you could create a decorator that allows you to optionally apply a layout to the story, by defining parameters.pageLayout = 'page' (or 'page-mobile'): :

import React from 'react';
 
export default {
  decorators: [
    // 👇 Defining the decorator in the preview file applies it to all stories
    (Story, { parameters }) => {
      // 👇 Make it configurable by reading from parameters
      const { pageLayout } = parameters;
      switch (pageLayout) {
        case 'page':
          return (
            // Your page layout is probably a little more complex than this ;)
            <div className="page-layout"><Story /></div>
          );
        case 'page-mobile':
          return (
            <div className="page-mobile-layout"><Story /></div>
          );
        case default:
          // In the default case, don't apply a layout
          return <Story />;
      }
    },
  ],
};

Using decorators to provide data

If your components are “connected” and require side-loaded data to render, you can use decorators to provide that data in a mocked way without having to refactor your components to take that data as an arg. There are several techniques to achieve this. Depending on exactly how you are loading that data. Read more in the building pages in Storybook section.

Story decorators

To define a decorator for a single story, use the decorators key on a named export:

import { Button } from './Button';
 
export default {
  component: Button,
};
 
export const Primary = {
  decorators: [
    (Story) => (
      <div style={{ margin: '3em' }}>
        {/* 👇 Decorators in Storybook also accept a function. Replace <Story/> with Story() to enable it  */}
        <Story />
      </div>
    ),
  ],
};

It is useful to ensure that the story remains a “pure” rendering of the component under test and that any extra HTML or components are used only as decorators. In particular the Source Doc Block works best when you do this.

Component decorators

To define a decorator for all stories of a component, use the decorators key of the default CSF export:

import { Button } from './Button';
 
export default {
  component: Button,
  decorators: [
    (Story) => (
      <div style={{ margin: '3em' }}>
        {/* 👇 Decorators in Storybook also accept a function. Replace <Story/> with Story() to enable it  */}
        <Story />
      </div>
    ),
  ],
};

Global decorators

We can also set a decorator for all stories via the decorators export of your .storybook/preview.js file (this is the file where you configure all stories):

import React from 'react';
 
export default {
  decorators: [
    (Story) => (
      <div style={{ margin: '3em' }}>
        {/* 👇 Decorators in Storybook also accept a function. Replace <Story/> with Story() to enable it  */}
        <Story />
      </div>
    ),
  ],
};

Decorator inheritance

Like parameters, decorators can be defined globally, at the component level, and for a single story (as we’ve seen).

All decorators relevant to a story will run in the following order once the story renders:

• Global decorators, in the order they are defined
• Component decorators, in the order they are defined
• Story decorators, in the order they are defined