Solution
var myForm = document.getElementById('myForm');
formData = new FormData(myForm);
// Find a element with id="myTable":
var table = document.getElementById("myTable");
// Create an empty element and add it to the 1st position of the table:
var row = table.insertRow(0);
// Insert new cells ( elements) at the 1st and 2nd position of the "new" element:
var cell1 = row.insertCell(0);
var cell2 = row.insertCell(1);
// Add some text to the new cells:
cell1.innerHTML = "NEW CELL1";
cell2.innerHTML = "NEW CELL2";