let data = new FormData()
        data["json"] = JSON.stringify(mydata);
        fetch(url, {
            method: 'POST',
            credentials: 'include',
            body: data
        }).then((res)=>{
            // ....
        }).catch(
//....
);export async function post(req, res, next) {
    console.log(req.body)
    res.writeHead(200, {
        'Content-Type': 'application/json'
    });
} 
  
  export async function post(req, res, next) {
    console.log(req.body) // вот для этого необходим body-parser
    res.writeHead(200, {
        'Content-Type': 'application/json'
    });
}