Retorna rango de fecha(inicio - fin) de un mes

main.ts

getWeeksInMonth(year: number, month: number) {

        const weeks = [];
        const firstDay: Date = new Date(year, month, 1);
        const lastDay: Date = new Date(year, month + 1, 0);
        const daysInMonth: number = lastDay.getDate();
        let dayOfWeek: number = firstDay.getDay();
        let start: number;
        let end: number;

        for (let i = 1; i < daysInMonth + 1; i++) {

            if (dayOfWeek === 0 || i === 1) {
                start = i;
            }

            if (dayOfWeek === 6 || i === daysInMonth) {

                end = i;

                if (start !== end) {

                    weeks.push({
                        start: start,
                        end: end
                    });
                }
            }

            dayOfWeek = new Date(year, month, i).getDay();
        }

        return weeks;
    }