function SetFields()
{
      var FArray = new Array(FieldSet.length);
      for (var i = 0; i < FieldSet.length; i++)
      {
            FArray[i] = { ID = FieldSet[i].ID, Value = document.getElementById(FieldSet[i].ID).value };
      }
      alert(FArray.length);
}

var FieldSet;

let myObj = {id: 1, value: 2}