Function prefetchRoute

packages/dev/s2-docs/src/prefetch.ts:10–42

(pathname: string, priority: RequestPriority = 'low')

const prefetchPromises = new Map<string, Promise<ReactElement>>();

export function prefetchRoute(pathname: string, priority: RequestPriority = 'low') {
  let url = getRSCUrl(pathname);

  // Skip if already prefetched
  if (prefetchPromises.has(url)) {
    return;
  }

  if (priority === 'low' && 'connection' in navigator) {
    let conn: any = navigator.connection;
    if (conn.saveData || /2g/.test(conn.effectiveType)) {
      return;
    }
  }

  // Start prefetch and cache the promise
  const prefetchPromise = fetchRSC<ReactElement>(url, {priority});

  prefetchPromise
    .then(res => {
      // Remove from cache after 30 seconds (rely on browser cache for subsequent requests)
      // This is required so we can reuse the same promise on click.
      setTimeout(() => {
        prefetchPromises.delete(url);
      }, 30_000);
      return res;
    })
    .catch(() => {
      prefetchPromises.delete(url);
    });

  prefetchPromises.set(url, prefetchPromise);
}

export function getPrefetchedPromise(rscPath: string): Promise<ReactElement> | undefined {
  return prefetchPromises.get(rscPath);