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How can i read backend error message?

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Entlebucher Mountain Dog posted this in #help-forum
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Entlebucher Mountain DogOP
when i'm getting status 500 or 400 didn't get error message in the catch
what's wrong with my code ?
"use server";
import { api_url } from "@/config";
import { revalidateTag } from "next/cache";

export const addCategory = async (newCategory: FormData) => {
try {
const res = await fetch(${api_url}/category/, {
method: "POST",
body: newCategory,
});
revalidateTag("category");

return {
status: res.status,
data: null,
};
} catch (error) {
console.log(error);
}
};

12 Replies

Toyger
you have runtime logs at vercel https://vercel.com/docs/observability/runtime-logs
Flávio inácio
You can do this

if (!res.ok) {
throw new Error('Failed to fetch data')
}
@Flávio inácio You can do this if (!res.ok) { throw new Error('Failed to fetch data') }
Entlebucher Mountain DogOP
if i do that can i see the error that is sent from backend ?
You can eliminate this try/catch and using only

const res = await fetch(${api_url}/category/, { method: "POST", body: newCategory, }); const json = await res.json(); if (!res.ok) { console.error(json); return; } revalidateTag("category"); return { status: res.status, data: null, };
goodsie
I'm not sure the .json() will work if res.ok is false?? (lack of body)


const res = await fetch(`${ api_url }/category/`, {
  method: "POST",
  body: newCategory,
});

if (!res.ok) {
  res.status(500).json({ error: res.statusText });
}

const json = await res.json();
revalidateTag("category");
return json;
@goodsie I'm not sure the .json() will work if res.ok is false?? (lack of body) js const res = await fetch(`${ api_url }/category/`, { method: "POST", body: newCategory, }); if (!res.ok) { res.status(500).json({ error: res.statusText }); } const json = await res.json(); revalidateTag("category"); return json;
Flávio inácio
If you don't need the backend error message from the backend, then it's ok. Otherwise, you need "const json = await res.json();", before the if, to get the error message returning through the back
goodsie
I wasnt aware that .json() would even have value if !ok ?
Flávio inácio
It is important to remember that Next Js made an extension to the web fetch API
goodsie
odd.
When I make a fetch that does not succeed I get:
Uncaught SyntaxError SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

from trying to use res.json() when !res.ok
In this case