request.js

$.ajax( {
                type: 'POST',
                url: 'http://localhost:1337/sendMail',
                data: json,
                dataType: 'json',
                success: function () {
                    form.style.display = 'none';
                },
                error: function(jqXHR, textStatus, err) { //show error message
                    console.log('Error: '+textStatus+', err '+err);
                },
                fail: function( jqXHR, textStatus ) {
                    console.log( "Request failed: " + textStatus );
                }
            });