#useSwr in typescrpt

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wide gladeBOT
#

Hi @light sail. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

#

The error you're encountering might be due to several reasons. Here are a few possibilities based on the information provided in the extracts:

  1. Environment: The fetch function is a web API that is not available in some environments. If you're running this code in an environment where fetch is not defined, you'll encounter an error. For example, Node.js does not have a native fetch function. If you're running this code on the server-side in a Node.js environment, you'll need to import a package like node-fetch or isomorphic-fetch to use the fetch function.

  2. Scope: If the fetch function is not in the scope where your fetcher function is defined, you'll encounter an error. Make sure that fetch is defined in the same scope as fetcher or in a parent scope.

  3. Syntax: If there's a syntax error in your code, you'll encounter an error. The code you've provided seems syntactically correct, but if there's an error elsewhere in your code, it could cause this line to fail.

Without more specific information about the error message you're seeing, it's hard to diagnose the exact problem. I recommend checking the error message for more details. If the error message mentions that fetch is not defined, the issue is likely related to the environment or scope. If the error message points to a syntax error, you'll need to check your code for syntax mistakes.

Here's an example of how to use fetch in a Next.js application, based on the extracts:

# 
async function getData() {
 const res = await fetch('<https://api.example.com/...'>)
 // The return value is *not* serialized
 // You can return Date, Map, Set, etc.
 
 if (!res.ok) {
 // This will activate the closest `error.js` Error Boundary
 throw new Error('Failed to fetch data')
 }
 
 return res.json()
}
 
export default async function Page() {
 const data = await getData()
 
 return <main></main>
}

Source (https://nextjs.org/docs/app/building-your-application/data-fetching/fetching-caching-and-revalidating)

If you're still encountering issues, please provide more details about the error message and the context in which you're running this code.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@light sail kapa.ai is still learning and improving, please let us know how it did by reacting below

light sail
#

Why my I cant use this code?

const fetcher = (...args) => fetch(...args).then(res => res.json())

Error: A spread argument must either have a tuple type or be passed to a rest parameter.
@wide glade

wide gladeBOT
#

Let me check the knowledge base for you. One moment! :books:

#

The error message you're seeing is related to TypeScript. TypeScript is expecting a tuple type or a rest parameter for the spread argument ...args in your fetcher function.

In TypeScript, you need to specify the types of the arguments that your function accepts. In this case, fetch accepts two arguments: a RequestInfo and an optional RequestInit. Here's how you can type your fetcher function:

const fetcher = (url: RequestInfo, init?: RequestInit) => fetch(url, init).then(res => res.json())

If you want to keep using the spread operator, you can define args as an array of any type:

const fetcher = (...args: any[]) => fetch(...args).then(res => res.json())

However, this will lose the type safety benefits of TypeScript. It's generally better to explicitly type your function arguments if you know what types they should be.

Here's an example of how to use fetch in a Next.js application, based on the extracts:

async function getData() {
 const res = await fetch('<https://api.example.com/...'>)
 // The return value is *not* serialized
 // You can return Date, Map, Set, etc.
 
 if (!res.ok) {
 // This will activate the closest `error.js` Error Boundary
 throw new Error('Failed to fetch data')
 }
 
 return res.json()
}
 
export default async function Page() {
 const data = await getData()
 
 return <main></main>
}

Source (https://nextjs.org/docs/app/building-your-application/data-fetching/fetching-caching-and-revalidating)

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@light sail kapa.ai is still learning and improving, please let us know how it did by reacting below

light sail
#

@wide glade
How to set added type to an res.json()?

wide gladeBOT
#

Let me check the knowledge base for you. One moment! :books:

#

In Next.js, you can add TypeScript types to the res.json() method by importing the NextApiResponse type from next. You can then use this type to specify the shape of the response data. Here's an example:

import type { NextApiRequest, NextApiResponse } from 'next'
 
type ResponseData = {
 message: string
}
 
export default function handler(
 req: NextApiRequest,
 res: NextApiResponse<ResponseData>
) {
 res.status(200).json({ message: 'Hello from Next.js!' })
}

In this example, ResponseData is a type that represents the shape of the response data. The res parameter is typed as NextApiResponse<ResponseData>, which means that the json method expects an object that matches the ResponseData type.

Please note that the body of NextApiRequest is any because the client may include any payload. You should validate the type/shape of the body at runtime before using it. Source (https://nextjs.org/docs/pages/building-your-application/routing/api-routes)

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: