function prepareText(tweenProp, value) {
  if (tweenProp === 'number') {
    return parseFloat(value);
  }
  // empty strings crash the update function
  return value === '' ? ' ' : value;
}
Returns the property tween object.
@param {string} tweenProp the property name
@param {string} value the property value
@returns {number | string} the property tween object