@primer/primitives/dist/build/transformers/dimensionToRem.js

Typography, spacing, and color primitives for Primer design system

import { isDimension } from '../filters/index.js';
/**
 * @description base font size from options or 16
 * @param options
 * @returns number
 */
const getBasePxFontSize = (options) => (options && options.basePxFontSize) || 16;
/**
 * @description checks if token value has a specific unit
 * @param value token value
 * @param unit unit string like px or value
 * @returns boolean
 */
const hasUnit = (value, unit) => {
    if (typeof value === 'number') {
        return false;
    }
    return value.indexOf(unit) > -1;
};
/**
 * @description converts dimension tokens value to `rem`, ignores `em` as they are relative to the font size of the parent element
 * @type value transformer — [StyleDictionary.ValueTransform](https://github.com/amzn/style-dictionary/blob/main/types/Transform.d.ts)
 * @matcher matches all tokens of $type `dimension`
 * @transformer returns a `rem` string
 */
export const dimensionToRem = {
    name: 'dimension/rem',
    type: 'value',
    transitive: true,
    filter: isDimension,
    transform: (token, config, options) => {
        const valueProp = options.usesDtcg ? '$value' : 'value';
        const baseFont = getBasePxFontSize(config);
        const floatVal = parseFloat(token[valueProp]);
        if (isNaN(floatVal)) {
            throw new Error(`Invalid dimension token: '${token.name}: ${token[valueProp]}' is not valid and cannot be transform to 'rem' \n`);
        }
        if (floatVal === 0) {
            return '0';
        }
        if (hasUnit(token[valueProp], 'rem') || hasUnit(token[valueProp], 'em')) {
            return token[valueProp];
        }
        return `${floatVal / baseFont}rem`;
    },
};