function getStyleForProperty(elem, propertyName) {
  let result = defaultValues[propertyName];
  const styleAttribute = elem.style;
  const computedStyle = getComputedStyle(elem) || elem.currentStyle;
  const styleValue = styleAttribute[propertyName] && !/auto|initial|none|unset/.test(styleAttribute[propertyName])
    ? styleAttribute[propertyName]
    : computedStyle[propertyName];

  if (propertyName !== 'transform' && (propertyName in computedStyle || propertyName in styleAttribute)) {
    result = styleValue;
  }

  return result;
}
getStyleForProperty

Returns the computed style property for element for .to() method.
Used by for the `.to()` static method.

@param {Element} elem
@param {string} propertyName
@returns {string}