Javascript 双位数时差

我想用两位数显示TravelTimeHoursDiff和TravelTimeMinutesDiff现在我的时间显示为7:0，我想显示为07:00

 if ($scope.DispatchStatus.ArrivalTime != undefined){
                var today = $rootScope.getSysDate().split(" ");
                var timeArrival = new Date(today[0] + ' ' + $scope.DispatchStatus.ArrivalTime);
                var TravelTime = new Date(today[0] + ' ' + $scope.Route.TravelTime);
                var timeArrivalHours = timeArrival.getHours();
                var TravelTimeHoursDiff = timeArrivalHours - TravelTime.getHours() ;
                var TravelTimeMinutesDiff = (timeArrival.getMinutes() - TravelTime.getMinutes());

                    if(TravelTimeHoursDiff < 0 || (TravelTimeHoursDiff <= 0 && TravelTimeMinutesDiff < 0) || (TravelTimeHoursDiff == 0 && TravelTimeMinutesDiff == 0)){                    
                        $scope.formvalidationbit = $scope.DispatchStatusAddForm[fieldName].$invalid = true;
                         angular.element('#' + fieldName).addClass('ng-invalid');
                         angular.element('#' + fieldName).removeClass('ng-valid');
                         $scope.DispatchStatusAddForm.$valid = false;
                         var errorbit = 1;

                    }else{
                        if (isNaN(TravelTimeHoursDiff)) {
                             TravelTimeHoursDiff = '--';
                         }
                         if (isNaN(TravelTimeMinutesDiff)) {
                             TravelTimeMinutesDiff = '--';
                         }
                         if(TravelTimeMinutesDiff <0){
                             TravelTimeMinutesDiff = TravelTimeMinutesDiff * (-1);
                         }
                         $scope.TravelTime = TravelTimeHoursDiff + ':' + TravelTimeMinutesDiff;
                    }
}

if（$scope.DispatchStatus.ArrivalTime！=未定义）{
var today=$rootScope.getSysDate（）.split（“”）；
var timeArrival=新日期（今天[0]+'+$scope.DispatchStatus.ArrivalTime）；
var TravelTime=新日期（今天[0]+'+$scope.Route.TravelTime）；
var timeArrivalHours=timeArrival.getHours（）；
var TravelTimeHoursDiff=timeArrivalHours-TravelTime.getHours（）；
var TravelTimeMinutesDiff=（timeArrival.getMinutes（）-TravelTime.getMinutes（））；
如果（TravelTimeHoursDiff<0 | | |）（TravelTimeHoursDiff只需将前导的
0
添加到小于
10
的值，类似于：

let addLeadingZero(v){
    return v < 10 ? ("0" + v) : v;
}
$scope.TravelTime = addLeadingZero(TravelTimeHoursDiff) + ':' + addLeadingZero(TravelTimeMinutesDiff);

让addLeadingZero（v）{
返回v<10？（“0”+v）：v；
}
$scope.TravelTime=addLeadingZero（TravelTimeHoursDiff）+'：'+addLeadingZero（TravelTimeMinutesDiff）；