How to convert a float into time in Javascript?

function convertNumToTime(number) {
    // Check sign of given number
    var sign = (number >= 0) ? 1 : -1;

    // Set positive value of number of sign negative
    number = number * sign;

    // Separate the int from the decimal part
    var hour = Math.floor(number);
    var decpart = number - hour;

    var min = 1 / 60;
    // Round to nearest minute
    decpart = min * Math.round(decpart / min);

    var minute = Math.floor(decpart * 60) + '';

    // Add padding if need
    if (minute.length < 2) {
    minute = '0' + minute; 
    }

    // Add Sign in final result
    sign = sign == 1 ? '' : '-';

    // Concate hours and minutes
    time = sign + hour + ':' + minute;

    return time;
}

console.log(convertNumToTime(11.15));
console.log(convertNumToTime(1.08));
console.log(convertNumToTime(-2.50));
console.log(convertNumToTime(2));
console.log(convertNumToTime(0.40));

function NumToTime(num) { 
    var hours = Math.floor(num / 60);  
    var minutes = num % 60;
    if (minutes + ''.length < 2) {
        minutes = '0' + minutes; 
    }
    return hours + ":" + minutes;
}

console.log(NumToTime(88));
console.log(NumToTime(350));
console.log(NumToTime(1236));