main.js

$("body.refunds.home.rmcuser #idf").on(
            "keypress",
            function (e) {
                var charCode = (typeof e.which == "undefined") ? e.keyCode : e.which;
                var charStr = String.fromCharCode(charCode);
                return /\d/.test(charStr) // number
                       || e.keyCode == 37 || e.keyCode == 39 // left and right arrows
                       || e.keyCode == 36 || e.keyCode == 35 // home and end
                       || e.keyCode == 8 || e.keyCode == 46 // backspace and delete
                       || (e.ctrlKey && (charStr == 'v' || charStr == 'V')); // paste
            }