请问，在函数参数里面加：和？ 是什么意思？
还有function 定义函数后面是不是{}，而是：
es6的数据解构中没看到，是我看漏了吗？求各大神指导一下

export function createRoute (
  record: ?RouteRecord,
  location: Location,
  redirectedFrom?: Location
): Route {
  const route: Route = {
    name: location.name || (record && record.name),
    meta: (record && record.meta) || {},
    path: location.path || '/',
    hash: location.hash || '',
    query: location.query || {},
    params: location.params || {},
    fullPath: getFullPath(location),
    matched: record ? formatMatch(record) : []
  }
  if (redirectedFrom) {
    route.redirectedFrom = getFullPath(redirectedFrom)
  }
  return Object.freeze(route)
}