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49 lines
1.2 KiB
49 lines
1.2 KiB
// @flow
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import PolishedError from '../internalHelpers/_errors'
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const cssVariableRegex = /--[\S]*/g
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/**
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* Fetches the value of a passed CSS Variable.
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*
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* Passthrough can be enabled (off by default) for when you are unsure of the input and want non-variable values to be returned instead of an error.
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*
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* @example
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* // Styles as object usage
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* const styles = {
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* 'background': cssVar('--background-color'),
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* }
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*
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* // styled-components usage
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* const div = styled.div`
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* background: ${cssVar('--background-color')};
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* `
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*
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* // CSS in JS Output
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*
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* element {
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* 'background': 'red'
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* }
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*/
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export default function cssVar(cssVariable: string, passThrough?: boolean): string | number {
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if (!cssVariable || !cssVariable.match(cssVariableRegex)) {
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if (passThrough) return cssVariable
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throw new PolishedError(73)
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}
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let variableValue
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/* eslint-disable */
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/* istanbul ignore next */
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if (typeof document !== 'undefined' && document.documentElement !== null) {
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variableValue = getComputedStyle(document.documentElement).getPropertyValue(cssVariable)
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}
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/* eslint-enable */
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if (variableValue) {
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return variableValue.trim()
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} else {
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throw new PolishedError(74)
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}
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}
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