addDuration(durationA, durationB) {
		let durA = durationA.match(/^(\d{2,}):(\d{2}):(\d{2}),(\d{3})$/);
		let durB = durationB.match(/^(\d{2,}):(\d{2}):(\d{2}),(\d{3})$/);
		let time = [];
		let formattedTime;

		// milliseconds
		durA[4] = durA[4].replace(/^0+/, '');
		durB[4] = durB[4].replace(/^0+/, '');
		time[4] = Number(durA[4]) + Number(durB[4]);
		if (time[4] >= 1000) {
			time[4] -= 1000;
			durB[3]++;
		}

		// seconds
		time[3] = Number(durA[3]) + Number(durB[3]);
		if (time[3] >= 60) {
			time[3] -= 60;
			durB[2]++;
		}

		// minutes
		time[2] = Number(durA[2]) + Number(durB[2]);
		if (time[2] >= 60) {
			time[2] -= 60;
			durB[1]++;
		}

		// hours
		time[1] = Number(durA[1]) + Number(durB[1]);

		// string format
		formattedTime = `${time[1]}:`;
		if (formattedTime.length < 3) formattedTime = '0' + formattedTime;

		formattedTime += `00${time[2]}:`.slice(-3);
		formattedTime += `00${time[3]},`.slice(-3);

		time[4] = time[4].toString().slice(0,3);
		while (time[4].length < 3) time[4] = '0' + time[4];
		formattedTime += time[4];

		return formattedTime;
	}
Compute (durationA + durationB)

@param {String} durationA
@param {String} durationB
@return {string}