const data = Object.fromEntries(formData);

How to add an array to the last in this object:

const formElment = document.querySelector(".form");

formElment.addEventListener("submit", (event) => {
  event.preventDefault();

  var array = [];
  var checkboxes = document.querySelectorAll("input[type=checkbox]:checked");

  for (var i = 0; i < checkboxes.length; i++) {
    array.push(checkboxes[i].value);
    console.log(checkboxes[i].id);
  }

  const formData = new FormData(formElment);
  const data = Object.fromEntries(formData);
  
  console.log(data);

});

I used eventlistner for get form data and checkbox=checked. So now I want add those selected checkbox id to the end of the object and send through an API.