Ajax concat FormData form + parameters

For Ajax FormData add extra parameters to pass data in PHP file,

See below example for that,

var fd = new FormData(document.getElementById("form"));
fd.append("CustomField", "This is some extra data");
$.ajax({
  url: "stash.php",
  type: "POST",
  data: fd,
  processData: false,  // tell jQuery not to process the data
  contentType: false   // tell jQuery not to set contentType
});

Enjoy!