Need help using fetch POST - extra data when sending a post? why?

Question

JavaScript

Hello, I have a view code

var formData = new FormData();
formData.append('var', 'value');
                    fetch(url,
                        {
                            method: 'POST',
                            headers: {
                                'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8;'
                            },
                            body:formData
                        }
                    )
                        .then(data => {
                            if (data.ok) {
                                return data.json()
                            } else {
                              return   Promise.reject(data)
                            }
                        })
                        .then(data => console.log(data))
                        .catch(() => {
                            console.log('err');
                            }
                    );

and such data is sent to the server

how do I send normal data of the form key : value