Firebase Code inside a Next.js API Function

firebase.js

const firebase = require("firebase");
// Required for side-effects
require("firebase/firestore");

const firebaseConfig = { /* ... */ };

try {
  firebase.initializeApp(firebaseConfig);
} catch (error) {
  /*
   * We skip the "already exists" message which is
   * not an actual error when we're hot-reloading.
   */
  if (!/already exists/u.test(error.message)) {
    // eslint-disable-next-line no-console
    console.error("Firebase initialization error", error.stack);
  }
}

export default firebase;

increment-views.js

import firebase from "../../lib/firebase";

export default async (req, res) => {
  try {
    if (!req.query.id) {
      return res.status(400).json({
        error: 'Missing "id" query parameter'
      });
    }

    const db = firebase.firestore();
    const doc = await db.collection("views").doc(req.query.id).get();

    let count = 0;
    if (doc.exists) {
      count = doc.data().count + 1;
    } else {
      console.log("document does not exist");
    }

    await db.collection("views").doc(req.query.id).set({
      id: req.query.id,
      count
    });

    return res.status(200);
  } catch (error) {
    console.error(error);
    return res.status(error.status || 500).end(error.message);
  }
};