Why does this IF statement freeze my browser? [on hold]

if (isFirstLoad) {
                _agendaFullOption.refetchEvent();
                this.getAgendaData(id, sessionStorage["intervalTime"] ? JSON.parse(sessionStorage["intervalTime"]) : {}, false);
            }

I am working on a project where I have to use a calendar agenda, each time i access the calendar agenda page and this IF statement isn't in comments my browser freezes. When i comment this statement it works just fine, not really sure why..