Please share the form structure where you are sending the data from. There are ways to setup the NAME of input elements to create a complex JSON on the server request data.
Something like name="ids['values][]" should make the $_POST look like what you want.
Thanks @sid - unfortunately nodeJS doesn’t interpret this kind of structure very well, I’ve spent a bit of time on this with patrick and he confirmed as such - is this the only way you can think of achieving this?
Note - bit of an error on my part, I’m not using .stringified for this particular field, that was for the field below - I’m setting the value of an array in the text area, which still outputs th same result: id1,id2,id3,id4 in the field before being sent to the backend.