FormData Returns empty data on form submission in react

I think you need to fetch it through looping. Try this

  var formData = new FormData(target);

   for (var [key, value] of formData.entries()) { 
   console.log(key, value);
  }

Hope it works.

handleSubmit should be like this.

handleSubmit(event) {
    event.preventDefault();
    const data = new FormData(event.target);
    fetch('my-api', {
      method: 'POST',
      body: data,
    });
  }

After form submit, in network tab you will find form data with key-value.

If you want to access single value,

const username = data.get('username');