TimesheetCalculator.js

class TimesheetCalculator {
    constructor(shiftDurations) {
        this.shiftDurations = shiftDurations;
    }

    getCalculatedTime() {
        const durationsWithMinsInDecimal = this.shiftDurations.split(' ');
        const durationsWithMins = [];
        for (let duration of durationsWithMinsInDecimal) {
            const hourPart = duration.split('.')[0];
            let minutes;
            if (duration.includes('.')) {
                let minsAsDecimal = duration.split('.')[1];
                minutes = Math.round(Number.parseFloat('.' + minsAsDecimal) * 60);
                const minPartAsString = minutes.toString();
                const paddedMinPart = ('00' + minPartAsString).substring(minPartAsString.length);
                durationsWithMins.push(hourPart + ':' + paddedMinPart);
            } else {
                durationsWithMins.push(hourPart + ':00');
            }
        }
        return durationsWithMins
    }
}

const a = new TimesheetCalculator('7.56 8.22 8.08 8.5 9.9');
const b = a.getCalculatedTime();

console.log(b);