let currentTime = new Date();

let currentHour = parseInt(currentTime.getHours());

let availableDates = ["10:00 PM", "08:00 AM", "12:00 AM", "01:00 AM", "12:00 PM", "03:00 AM", "07:00 AM", "06:00 PM"];

let convertedHours = availableDates.map((date) => {

    return date.split(' ')[0] < 12 ? date.split(' ')[0] : parseInt(date.split(' ')[0]) + parseInt(12);

});

​

let getNearestTime = (convertedHours, currentHour) => {

    let nearestTime;

    let minValue = convertedHours[0] > currentHour ? (convertedHours[0] - currentHour) : (currentHour - convertedHours[0]);

    convertedHours.reduce((minVal, hour) => {

        let hourDiff = (currentHour > hour) ? currentHour - hour : hour - currentHour;

        if(hourDiff <= minVal) {

            nearestTime = hour;

            return hourDiff;

        } else {

            return minVal;

        }

    }, minValue)

​

    return availableDates[convertedHours.indexOf(nearestTime)];

};

​

console.log(getNearestTime(convertedHours, currentHour));