storybook/docs/essentials/toolbars-and-globals.md

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Toolbars & globals

Storybook ships with toolbar items to control the viewport and background the story renders in. You can also create your own toolbar items which control special “globals” which you can then read to create decorators to control story rendering.

Globals

Globals in Storybook represent “global” (as in not story-specific) inputs to the rendering of the story. As they aren’t specific to the story, they aren’t passed in the args argument to the story function (although they are accessible as context.globals), but typically you use them in decorators which apply to all stories.

When the globals change, the story re-renders and the decorators rerun with the new values. The easiest way to change globals is to create a toolbar item for them.

Global types and the toolbar annotation

Storybook has a simple, declarative syntax for configuring toolbar menus. In your .storybook/preview.js, you can add your own toolbars by creating globalTypes with a toolbar annotation:

<CodeSnippets paths={[ 'common/storybook-preview-configure-globaltypes.js.mdx', ]} />

As globals are global you can only set globalTypes in .storybook/preview.js.

When you start your Storybook, you should see a new dropdown in your toolbar with options light and dark.

Create a decorator

We have a global defined, let's wire it up! We can consume our new theme global in a decorator using the context.globals.theme value.

For example, suppose you are using styled-components. You can add a theme provider decorator to your .storybook/preview.js config:

<CodeSnippets paths={[ 'common/storybook-preview-use-global-type.js.mdx', ]} />

Advanced usage

So far we've managed to create and consume a global inside Storybook.

Now let's take a look at a more complex example. Let's suppose we wanted to implement a new global called locale for internationalization, which shows a flag on the right side of the toolbar.

In your .storybook/preview.js, add the following:

<CodeSnippets paths={[ 'common/storybook-preview-locales-globaltype.js.mdx', ]} />

By adding the configuration element right, the text will be displayed on the right side in the toolbar menu, once you connect it to a decorator.

Here's a list of the configuration options available.

MenuItem	Type	Description	Required
value	String	The string value of the menu that gets set in the globals	Yes
title	String	The main text of the title	Yes
left	String	A string that gets shown in left side of the menu	No
right	String	A string that gets shown in right side of the menu	No
icon	String	An icon that gets shown in the toolbar if this item is selected	No

Consuming globals from within a story

We recommend consuming globals from within a decorator and define a global setting for all stories.

But we're aware that sometimes it's more useful to use toolbar options in a per-story basis.

Using the example above, you can modify any story to retrieve the Locale global from the story context:

<CodeSnippets paths={[ 'common/my-component-story-use-globaltype.js.mdx', 'common/my-component-story-use-globaltype.mdx.mdx', ]} />

In Storybook 6.0, if you set the global option passArgsFirst: false for backwards compatibility, the story context is passed as the first argument:

<CodeSnippets paths={[ 'common/my-component-story-use-globaltype-backwards-compat.js.mdx', ]} />

Consuming globals from within an addon

If you're working on a Storybook addon and you need to retrieve globals. You can do so, The @storybook/api package provides a hook for this scenario, you can use the useGlobals() hook to retrieve any globals you want.

Using the ThemeProvider example above, you could expand it to display which current theme is being shown inside a panel like so:

<CodeSnippets paths={[ 'common/addon-consume-globaltype.js.mdx', ]} />