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Parameters |
Parameters are a set of static, named metadata about a story, typically used to control the behavior of Storybook features and addons.
Available parameters are listed in the parameters API reference.
For example, let’s customize the backgrounds addon via a parameter. We’ll use parameters.backgrounds to define which backgrounds appear in the backgrounds toolbar when a story is selected.
We can set a parameter for a single story with the parameters key on a CSF export:
<CodeSnippets paths={[ 'angular/parameters-in-story.ts.mdx', 'web-components/parameters-in-story.js.mdx', 'web-components/parameters-in-story.ts.mdx', 'common/parameters-in-story.js.mdx', 'common/parameters-in-story.ts.mdx', ]} usesCsf3 csf2Path="writing-stories/parameters#snippet-component-story-custom-params" />
We can set the parameters for all stories of a component using the parameters key on the default CSF export:
<CodeSnippets paths={[ 'angular/parameters-in-meta.ts.mdx', 'web-components/parameters-in-meta.js.mdx', 'web-components/parameters-in-meta.ts.mdx', 'common/parameters-in-meta.js.mdx', 'common/parameters-in-meta.ts.mdx', ]} />
We can also set the parameters for all stories via the parameters export of your .storybook/preview.js file (this is the file where you configure all stories):
<CodeSnippets paths={[ 'common/parameters-in-preview.js.mdx', 'common/parameters-in-preview.ts.mdx', ]} />
Setting a global parameter is a common way to configure addons. With backgrounds, you configure the list of backgrounds that every story can render in.
The way the global, component and story parameters are combined is:
- More specific parameters take precedence (so a story parameter overwrites a component parameter which overwrites a global parameter).
- Parameters are merged so keys are only ever overwritten, never dropped.
The merging of parameters is important. It means it is possible to override a single specific sub-parameter on a per-story basis but still retain the majority of the parameters defined globally.
If you are defining an API that relies on parameters (e.g. an addon) it is a good idea to take this behavior into account.