500 (Internal Server Error) in redux-form method "PUT"

Question

I have some problem with PUT request in my reaсt app. I'm using redux-form with standart fetch request. When I send my request I got error: PUT http://localhost:8080/auth 500 (Internal Server Error) "SyntaxError: Unexpected token <" There is my code for fetch:

export default async function submit(fields, dispatch) {
    console.trace()
    const {email, fullName, company, industry, phone} = fields
    let errors
    if (!email)
        errors = {
            ...errors,
            email: 'Email cannot be empty'
        }; else if (!/[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}/i.test(email))
        errors = {...errors, email: 'Email seems invalid'};

    if (!fullName)
        errors = {...errors, fullName: 'Full name cannot be empty'};

    if (!company)
        errors = {...errors, company: 'Company name cannot be empty'};

    if (!industry)
        errors = {...errors, industry: 'Industry should be selected'};

    if (errors) {
        return Promise.reject(errors)
    }
    const response = await fetch('/auth', {
        credentials: 'same-origin',
        method: 'PUT',
        body: Object.keys(fields)
            .filter(prop => fields[prop] !== undefined)
            .reduce((fd, prop) => {
                fd.append(prop, fields[prop])
                return fd
            }, new FormData())
    });
    if (response.ok) {
        console.log('good');
        console.log(response);
    } else {
        const data = await response.json();
        console.log('bad');
        console.log(response);
    }
}

What can be wrong with it?

Answer 1

This isn't really related to redux-form, unless when you put a console.log(fields) before your fetch() call, you see something strange.

This is a serializing JSON into a FormData question. That said, I can't really see anything wrong with your "reduce into FormData" code. Maybe save that to a variable and output it to the console?

Either that, or there could be some problem on the server side where it is not expecting the data in that structure. I usually send stuff in plain JSON, but then I have full stack control.