Receiving JSON via AJAX in controller function

[Paul Ellis]

I have some JS which sends data from a row in a grid to the server as JSON.

The controller function receives the JSON in a request.vars key (not a value). This is awkward to find if there are other request.vars. Currently I am testing for lengths over 10. This was a quick hot fix because I added a request.var which is passed around the app and broke all of the ajax.

Is there a way I can change the JS that the JSON is either:
1 - received as a value in request.vars with a given key so I know exactly where it will be.
2 - received in another way that the goal is still achieved.

I tried to use the JS FormData object type but can't find it server side.

The web2py ajax function almost does what I want, but:
1 - I have to give it a Name rather than an ID. I guess this is because it was built to be used with forms.
2 - What the page does with the returned JSON will become more complex in future.

function updateRow(row, action = 'update'){
    // console.log('Update Row Called');
    var poiId = row.prop('id');
    var qty = row.find('[name="quantity"]').val() || 0;
    var disc = row.find('[name="discount"]').val() || 0;
    var mnthDisc = row.find('[name="monthlydiscount"]').val() || 0;
    var opt = row.find('[name="optional"]').prop('checked');
    var oid = document.getElementById('oid');
    var offerId = oid.getAttribute('name');
    var cid = document.getElementById('cid');
    var custId = cid.getAttribute('name');
   
    body = {
        'action' : action,
        'cid' : custId,
        'offer_id' : offerId,
        'poiId' : poiId,
        'discount' : disc,
        'monthlydiscount' : mnthDisc,
        'optional' : opt,
        'quantity' : qty,
    };
   
    var xhttp = new XMLHttpRequest();
   
    xhttp.open('POST', '/offer/ajax_update_offer', true);
   
    xhttp.onreadystatechange = function() {
        // console.log(this.readyState);
        // if (this.readyState == 4) {
            // console.log(this);
        // };
        if (this.readyState == 4 && this.status == 200) {
            var rObj = JSON.parse(this.responseText);
            if (rObj.status == "failed"){
                location = rObj.url;
            };
            if (rObj.status == "deleted") {
                $('#'+rObj.poiId).remove();
            };
            document.getElementById('purchase_running_total').innerText = rObj.pTotalStr
            document.getElementById('monthly_running_total').innerText = rObj.mTotalStr
            var selectedLi = $('.w2p_flash')
            selectedLi.html(rObj.flash).slideDown({duration: 1000, queue: false})
                .fadeOut({duration: 2000, queue: false})
                .promise().done(function() {
                selectedLi.hide();
            });
         
        };
    };
    xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xhttp.send(JSON.stringify(body));