frontend/node_modules/@mui/system/modern/cssVars/createGetCssVar.js

/**
 * The benefit of this function is to help developers get CSS var from theme without specifying the whole variable
 * and they does not need to remember the prefix (defined once).
 */
export default function createGetCssVar(prefix = '') {
  function appendVar(...vars) {
    if (!vars.length) {
      return '';
    }
    const value = vars[0];
    if (typeof value === 'string' && !value.match(/(#|\(|\)|(-?(\d*\.)?\d+)(px|em|%|ex|ch|rem|vw|vh|vmin|vmax|cm|mm|in|pt|pc))|^(-?(\d*\.)?\d+)$|(\d+ \d+ \d+)/)) {
      return `, var(--${prefix ? `${prefix}-` : ''}${value}${appendVar(...vars.slice(1))})`;
    }
    return `, ${value}`;
  }

  // AdditionalVars makes `getCssVar` less strict, so it can be use like this `getCssVar('non-mui-variable')` without type error.
  const getCssVar = (field, ...fallbacks) => {
    return `var(--${prefix ? `${prefix}-` : ''}${field}${appendVar(...fallbacks)})`;
  };
  return getCssVar;
}