I had this same issue before. If you are using the App directory, I have found that you have to do responses along the lines of:

return NextResponse.json({ status: (statuscode), message: (message) })

That might work, however I know you are using TypeScript and that you have to give the 'res' object a type of 'NextResponse'. I wasn't using TypeScript when I ran into this same error so I had to return what's provided in the code block above.

Hope this helps.

Thank you @New Zealand Heading Dog . Really appreciate you for telling me this, I will look into this. 🙂

the reason is that in app router route handlers you don't have res. in fact you don't have the express req either, you have the native req (Request) object instead. basically the syntaxes are completely different. see https://nextjs.org/docs/app/building-your-application/routing/router-handlers

hmm, very interesting, thanks @joulev You both are heros, have been struggling with this for a bit and the morning sun is already up.. :p

But I think I am using this correctly, I am sharing the whole file under here, so you understand how the req and res are being setup.

import type { NextApiRequest, NextApiResponse } from 'next';
import Stripe from 'stripe';

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY ?? '', {
  apiVersion: '2022-11-15',
});

console.log('outside the const handler!');

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  if (req.method !== 'POST') {
    return res.status(405).end();
  }
  try {
    const { price, quantity, items } = req.body;
    const lineItems = items
      ? items.map((item: any) => ({
          price: item.id,
          quantity: item.quantity,
        }))
      : [
          {
            price,
            quantity,
          },
        ];
    console.log('logging the req.headers.origin:');

    console.log(`${req.headers.origin}`);
    const session = await stripe.checkout.sessions.create({
      payment_method_types: ['card'],
      line_items: [
        {
          price: 'price_1N2UwFHjh6rwfnNSgLo5XwJs',
          quantity: 1,
        },
      ],
      // line_items: lineItems,
      mode: 'payment',
      success_url: `http://localhost:3000/result?session_id={CHECKOUT_SESSION_ID}`,
      cancel_url: `http://localhost:3000/cancel`,
      automatic_tax: { enabled: true },
    });
    if (items) {
      res.status(200).json({
        url: session.url,
      });
    } else {
      res.redirect(301, session.url ?? '');
    }
  } catch (e: any) {
    console.log(e);
    res.status(e.statusCode || 500).json({
      message: e.message,
    });
  }
}

@joulev

No you arent. It is not req: NextRequest, res: NextResponse. Check the documentation again. You don’t have res passed as a function param

Thank you!