jqGrid Button Formatter Bootstrap Modal Confirm Multiple Callbacks

Question

Hello i try to use a confirm Bootstrap Modal in a Button Formatter jqgrid

function buttonFormatter(cellvalue, options, rowobject)
{
    var id = rowobject.Id;
    return '<button id="button1_'+ id+ '"class="btn btn-danger btn-large" style="width:100%" onclick="buttonClick(this.id); return false;"><i class="fa fa-times"></i> ModalPopupShow</button>';    
}

function buttonClick(buttonId) 
{
    var res = buttonId.split("_");
    var id = res[res.length - 1];    

    $('#modal1').modal('show');

    var modalConfirm = function (callback) {

        $("#buttonModal1").on("click", function (e) {
            callback(true);
            $("#modal1").modal('hide');
        });

        $("#buttonModal2").on("click", function () {
            callback(false);
            $("#modal1").modal('hide');
        });
    };

    modalConfirm(function (confirm) {
        if (confirm) {
            alert("confirmado - " + id);
        } else {
            alert("Não confirmado");
        }
    });    
}

But I have multiple callbacks. I click once show one alert if i click another time two alerts, another click three alerts and so on...

What is the best way to avoid this behavior?

Tnks