Helper function for setting cache control from HTTP server responses

setCacheControl.ts

import { ServerResponse } from "http";

interface CacheControlConfig {
  sMaxAge?: number;
  maxAge?: number;
  staleWhileRevalidate?: boolean | number;
  publicCache?: boolean;
  privateCache?: boolean;
  immutable?: boolean;
  noCache?: boolean;
  noStore?: boolean;
}

export const setCacheControl = ({
  sMaxAge,
  maxAge,
  staleWhileRevalidate,
  publicCache,
  privateCache,
  immutable,
  noCache,
  noStore,
}: CacheControlConfig) => async (res: ServerResponse) => {
  if (noCache && immutable) {
    throw Error("You cannot use no-cache in-conjunction with immutable.");
  }

  const properties: string[] = [];

  if (publicCache) {
    properties.push("public");
  }

  if (privateCache) {
    properties.push("private");
  }

  if (noCache) {
    properties.push("no-cache");
  }

  if (noStore) {
    properties.push("no-store");
  }

  if (typeof sMaxAge !== "undefined") {
    properties.push(`s-maxage=${sMaxAge}`);
  }

  if (typeof maxAge !== "undefined") {
    properties.push(`max-age=${maxAge}`);
  }

  if (typeof staleWhileRevalidate === "number") {
    properties.push(`stale-while-revalidate=${staleWhileRevalidate}`);
  }

  if (typeof staleWhileRevalidate === "boolean" && staleWhileRevalidate) {
    properties.push(`stale-while-revalidate`);
  }

  const header = properties.join(", ");

  res.setHeader("Cache-Control", header);
};