function stringifyClass (value) {
  if (Array.isArray(value)) {
    return stringifyArray(value)
  }
  if (isObject(value)) {
    return stringifyObject(value)
  }
  if (typeof value === 'string') {
    return value
  }

  return ''
}
@link https://github.com/vuejs/vue/blob/dev/src/platforms/web/util/class.js