polished/lib/helpers/cssVar.js

A lightweight toolset for writing styles in Javascript.

"use strict";

exports.__esModule = true;
exports["default"] = cssVar;
var _errors = _interopRequireDefault(require("../internalHelpers/_errors"));
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }
var cssVariableRegex = /--[\S]*/g;

/**
 * Fetches the value of a passed CSS Variable in the :root scope, or otherwise returns a defaultValue if provided.
 *
 * @example
 * // Styles as object usage
 * const styles = {
 *   'background': cssVar('--background-color'),
 * }
 *
 * // styled-components usage
 * const div = styled.div`
 *   background: ${cssVar('--background-color')};
 * `
 *
 * // CSS in JS Output
 *
 * element {
 *   'background': 'red'
 * }
 */
function cssVar(cssVariable, defaultValue) {
  if (!cssVariable || !cssVariable.match(cssVariableRegex)) {
    throw new _errors["default"](73);
  }
  var variableValue;

  /* eslint-disable */
  /* istanbul ignore next */
  if (typeof document !== 'undefined' && document.documentElement !== null) {
    variableValue = getComputedStyle(document.documentElement).getPropertyValue(cssVariable);
  }
  /* eslint-enable */

  if (variableValue) {
    return variableValue.trim();
  } else if (defaultValue) {
    return defaultValue;
  }
  throw new _errors["default"](74);
}
module.exports = exports.default;