How to use returned JSON error in a JavaScript async fetch call

Question

I have an async fetch call which calls my backend to create a customer with an email address. If successful, the JSON returned is sent to a doNex

Answer 1

Personally I recommend the async/await syntax if the version you're using supports it. It really simplifies the code and allows you to easily use the try/catch syntax.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await#Browser_compatibility

It seems it doesn't work in IE though if that's a dealbreaker.

async function createCustomer(email) {
try {
    const response = await fetch("/api/create-customer", {
        method: "post",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ email: email })
    })
    if (response.ok) {
        const returnedData = await response.json();
        // if doNextThing is an async function, you can await it as well or just return it 
        doNextThing(returnedData);
    } else {
        throw {
            json: await response.json()
            status: response.status,
            statusText: response.statusText
        };
    }
} catch (requestErr) {
    // do what you like with the error
    // this will be called if you "throw" above or 
    // if fetch() rejects
    if (requestErr.json){
        console.error(JSON.stringify(requestErr.json));
    }
    console.error("Request err:" + requestErr);
}

}

Let me know if that helps.

Answer 2

You should be able to get the content using response.json() in the catch handler.