next.js/examples/with-firebase-hosting/firebaseFunctions.js

const { join } = require("path");
const { https } = require("firebase-functions");
const { default: next } = require("next");

const nextjsDistDir = join("src", require("./src/next.config.js").distDir);

const nextjsServer = next({
  dev: false,
  conf: {
    distDir: nextjsDistDir,
  },
});
const nextjsHandle = nextjsServer.getRequestHandler();

exports.nextjsFunc = https.onRequest((req, res) => {
  return nextjsServer.prepare().then(() => nextjsHandle(req, res));
});