polished/lib/helpers/remToPx.js

A lightweight toolset for writing styles in Javascript.

"use strict";

exports.__esModule = true;
exports["default"] = remToPx;
var _getValueAndUnit = _interopRequireDefault(require("./getValueAndUnit"));
var _errors = _interopRequireDefault(require("../internalHelpers/_errors"));
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }
var defaultFontSize = 16;
function convertBase(base) {
  var deconstructedValue = (0, _getValueAndUnit["default"])(base);
  if (deconstructedValue[1] === 'px') {
    return parseFloat(base);
  }
  if (deconstructedValue[1] === '%') {
    return parseFloat(base) / 100 * defaultFontSize;
  }
  throw new _errors["default"](78, deconstructedValue[1]);
}
function getBaseFromDoc() {
  /* eslint-disable */
  /* istanbul ignore next */
  if (typeof document !== 'undefined' && document.documentElement !== null) {
    var rootFontSize = getComputedStyle(document.documentElement).fontSize;
    return rootFontSize ? convertBase(rootFontSize) : defaultFontSize;
  }
  /* eslint-enable */
  /* istanbul ignore next */
  return defaultFontSize;
}

/**
 * Convert rem values to px. By default, the base value is pulled from the font-size property on the root element (if it is set in % or px). It defaults to 16px if not found on the root. You can also override the base value by providing your own base in % or px.
 * @example
 * // Styles as object usage
 * const styles = {
 *   'height': remToPx('1.6rem')
 *   'height': remToPx('1.6rem', '10px')
 * }
 *
 * // styled-components usage
 * const div = styled.div`
 *   height: ${remToPx('1.6rem')}
 *   height: ${remToPx('1.6rem', '10px')}
 * `
 *
 * // CSS in JS Output
 *
 * element {
 *   'height': '25.6px',
 *   'height': '16px',
 * }
 */
function remToPx(value, base) {
  var deconstructedValue = (0, _getValueAndUnit["default"])(value);
  if (deconstructedValue[1] !== 'rem' && deconstructedValue[1] !== '') {
    throw new _errors["default"](77, deconstructedValue[1]);
  }
  var newBase = base ? convertBase(base) : getBaseFromDoc();
  return deconstructedValue[0] * newBase + "px";
}
module.exports = exports.default;