Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client about nextjs-course-app

[lancemccluskey]

I am getting this error too. I was able to fix it by adding `typeof window === 'undefined' to the conditional expression with writeHead. Now it looks like this:

  if (!response.ok && typeof window === 'undefined') {
    res.writeHead(302, { Location: '/notes' })
    res.end()
    return {props: {}}
  }

I am honestly now positive why you need this though.
@juicecultus

[aashiqahmed98]

Instead of strict equality (===) operator use Object,is() and le me know!

[slavo3dev]

I had a similar issue, but I was trying to do all with ts. When I convert all to js everything was working as should be

[armor009]

Can anyone explain what exactly is happening here?
This seems to cover intricacies of next.js and server responses.

[JasonNoonan]

Having the same error. However, if I log params as the first line of getServerSideProps, the function works. Some kind of timing issue where params is not ready when fetch tries to call it, maybe?

export async function getServerSideProps({params, req, res}) {
  console.log(params)
  const response = await fetch(`http://localhost:3000/api/note/${params.id}`)

  if (!response.ok) {
    res.writeHead(302, { Location: '/notes' })
    res.end()
    return {props: {}}
  }

  const {data} = await response.json()
  
  
  if (data) {
    return {
      props: {note: data}
    }
  }
}```

[BhumilModi]

try this it worked for me
export async function getServerSideProps({ params, req, res }) {
const response = await fetch(http://localhost:3000/api/note/${params.id});

if (!response.ok) {
return res.writeHead(302, { Location: "/notes" }).end();
}

const { data } = await response.json();

if (data) {
return {
props: { note: data },
};
}
}