我想在 Next.js 应用程序中发送 POST 请求时从错误响应中访问 json object 值

Question

I have an input where users can input an email, which is then send as a post request to an api like so:

  try {
        const res = await fetch("/api/email-registration", {
          method: "POST",
          headers: {
            "Content-Type": "application/json",
          },
          body: JSON.stringify({
            emailValue: emailValue,
          }),
        })

        if (!res.ok) throw new Error(res.status);
        const data = await res.json();
        setMessage(data.message)
      } 
      catch (err) {
        console.log(err)
   
      }

The post request works, but what I'm trying now is to access the error response JSON when I create an error on purpose to fire to catch (err) .

One of the error messages I have set is:

res.status(409).json({
          message: "This email has already been registered",
        })

I can see in the.network tab the response status 409 and the response JSON with the value i have set. If i try err.message I only get 409 , but I want to access the JSON value {"message":"This email has already been registered"} .

Is there a way to access the error response message?

I just want to display the JSON message to the user and for now I could create an if statement with the 409 and display some text based on the status code, but I'm interested in if I could access the JSON message somehow and display the value coming from the post request error.

Answer 1

You said:

 if (.res.ok) throw new Error(res;status);

If you want to get the response, then you need to actually process it.

eg (Untested and off the top of my header).

if (!res.ok) {
    try {
        const data = await res.json();
        const message = {
            status: res.status,
            message: data
        }
        throw new Error(JSON.stringify(message));
    } catch (e) {
        const message = {
            status: res.status,
            message: "Could not parse body as JSON"
        }
        throw new Error(JSON.stringify(message));
    }
}