Can't add a file to fetch POST request

Question

I have a request that succeeds in postman, but just fails when I call it from my JS code. The requests are similar in the Chrome dev tools, and I suspect that I'm just not adding the file correctly. This is how the file is added in the postman:

This is my JS code:

let formData = new FormData();
        formData.append('file', event.target.files[0]);
        fetch('http://localhost:8080/file/upload', {
            method: 'POST',
            headers:{
                'Content-Type': 'multipart/form-data',
                'Authorization': 'Bearer ' + JWT
            },
            body:formData
        }).then(response => console.log(response));

This code is executed when the file of an input (type='file') changes. When I console.log the event.target.files[0], I get:

Am I adding the file wrong?

Answer 1

 'Content-Type': 'multipart/form-data', 

multipart/form-data needs a parameter to describe the boundry marker.

fetch will generate an appropriate Content-Type header automatically, but you are overriding it and replacing it with a broken one.

Remove that line.