104-nextjs-backend.mdc

---
description: EXPLAIN how NextJS 15 backend methods work.
globs: *.ts, *.tsx
---
## Context

* NextJS 15 give us backend methods we should use.

## Header

Enable you to get the header of the request.

```tsx
import { headers } from 'next/headers'
 
export default async function Page() {
  const headersList = await headers()
  const userAgent = headersList.get('user-agent')
}
```


## Cookie

Enable you to get the cookie of the request.

```tsx
import { cookies } from 'next/headers'
 
export default async function Page() {
  const cookieStore = await cookies()
  const theme = cookieStore.get('theme')
  return '...'
}
```

To set a cookie, you must be in an [api-route.mdc](mdc:.cursor/rules/api-route.mdc) or [server-actions.mdc](mdc:.cursor/rules/server-actions.mdc) :

```tsx
'use server'
 
import { cookies } from 'next/headers'
 
export async function create(data) {
  const cookieStore = await cookies()
 
  cookieStore.set('name', 'lee')
  // or
  cookieStore.set('name', 'lee', { secure: true })
  // or
  cookieStore.set({
    name: 'name',
    value: 'lee',
    httpOnly: true,
    path: '/',
  })
}
```