WordPress fetch example

 const dataanak = new FormData();
  dataanak.append('action', 'tableaugettiket');
  dataanak.append('username', 'bi.admin');
  let ticket = new Promise(function (myResolve, myReject) {
    fetch(frontendajax.ajaxurl, {
      method: 'POST',
      // or 'PUT'
      body: dataanak
    }).then(response => response.json()).then(data => {
      console.log('tiket', data);
      myResolve(data);
    });
  });