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2.5.0 • Public • Published


If you’re interested in digging around in the internals of jsxstyle, you’ve come to the right place. jsxstyle only contains React- and preact-specific jsxstyle components. jsxstyle-utils exports the functions that provide specific features to both runtime jsxstyle and jsxstyle-webpack-plugin.

Core functionality

getStyleKeysForProps(props: object, pretty=false)

getStyleKeysForProps splits the provided object of props into separate style objects by pseudoclass, pseudoelement, and media query. CSS property names are alphabetised and converted to snake case with hyphenateStyleName, and property values are converted to CSS-friendly values with dangerousStyleValue. The return value is an object of separated style objects keyed with a specially-formatted key that, when sorted, will order each style object in the proper order. The returned object also provides a styleCacheKey property that represents the original props object. If the pretty param is set to true, non-essential whitespace (indentation and newlines) will be included in the output CSS.


getStyleCache returns an object consisting of four methods for manipulate a cache of styles:

  • cache.getClassName(props: object): takes an object of props and passes it through to getStyleKeysForProps. The styleCacheKey it receives from getStyleKeysForProps is hashed with stringHash and used as the base of a class name that represents the props object. If this generated class name is not present in the internal style cache, the class name is added to the cache and the corresponding styles provided by getStyleKeysForProps are added to the document with addStyleToHead. The generated class name is returned.

  • cache.reset(): sets the internal style cache object to a new object.

  • cache.injectOptions(options: object): allows the user to inject config options into the style cache. Available options:

    • onInsertRule(rule: string, props: object): function called each time a string of styles is added to the document. If provided, this function will be called once for each unique string of styles. Return false from onInsertRule to prevent the CSS rule from being added to the document head.
    • getClassName(styleKey: string, props: object): function that should return a CSS class name unique to the styleKey.
    • pretty: boolean: whether or not CSS output should contain non-essential whitespace.

Each component returned by a jsxstyle component factory calls cache.getClassName with the component’s props whenever the component receives props. The class/className prop of the returned element is set to the return value of getClassName.


addStyleToHead(rule: string)

addStyleToHead creates a style element and adds the provided rule param to the document head using sheet.insertRule.

dangerousStyleValue(name: string, value: any)

dangerousStyleValue converts the provided value according to what the name expects. Most notably, this function adds px suffixes to unitless properties (padding, margin, etc.). This is a slightly modified version of the dangerousStyleValue function that ships with React.

hyphenateStyleName(name: string)

hyphenateStyleName converts camelCased names to snake-case. Vendor prefixes are properly formatted. This is a slightly modified version of the hyphenateStyleName function that ships with React.

stringHash(content: string)

stringHash is a copy of Dark Sky’s string-hash module converted to ES module syntax.



An object of styles keyed by component name. This is the object representation of the components exported by jsxstyle.

Key Value
Block { display: 'block' }
Inline { display: 'inline' }
InlineBlock { display: 'inline-block' }
Row { display: 'flex', flexDirection: 'row' }
Col { display: 'flex', flexDirection: 'column' }
Grid { display: 'grid' }
Box null



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  • meyer
  • meyerbot