calculating time differences using moment.js - momentjs

Question

Friends,
I have an array containing checkins and checkouts times and need to calculate the spent time between these operations. For that I iterate through this table partitioning checkins from checkouts in two separated arrays, like that:
var checkins = [];
var checkouts = [];
var results = [];
var index;
for (index = 0; index < $scope.data.registries.length; ++index){
if ($scope.data.registries[index].rType == 0) {
checkins.push(moment($scope.data.registries[index].savedHour, "HH:mm:ss"));
}
else {
checkouts.push(moment($scope.data.registries[index].savedHour, "HH:mm:ss"));
}
}
After that I just iterate over checkins array, calculating the diffs and pushing it into the results array, like this:
for (index = 0; index < checkins.length; ++index){
if (index <= checkouts.length) {
results.push(moment.utc(checkouts[index]).diff(moment(checkins[index])));
}
}
So, now I have an array containing only the diff times, for each pair of checkin checkout. Now I just
make a sum of theses diffs... like this:
var total = null;
for (index = 0; index < results.length; ++index) {
if (index == 0){
total = moment(results[index]);
}
else{
total.add(results[index]);
}
}
if (results.length == 0) {
return "00 hour(s) and 00 minute(s)";
}
else {
return moment.utc(total).format("HH [ hour(s) and ] mm [ minute(s)]");
}
I'm not getting the correct amount of time.... for the following sample data:
checkin 07:32
checkout 07:34 ->
difference: 2 minutes
checkin 08:20
checkout 08:53 ->
difference: 33 minutes
I should have a total of 35 minutes, but
its always changing according to current time... for example, here now is 10:51 (am)
and this function is returning 2h and 37m
I dont see what is wrong... could someone point it out?

Answer 1

A few things:
You're subtracting UTC against local time:
moment.utc(checkouts[index]).diff(moment(checkins[index]))
^^^^^^^^^^ ^^^^^^
Either both values should be UTC, or both values should be local.
You said your inputs were time-only values. Keep in mind that when you don't specify a date, the current date is assumed. If you are working with local times on a day that has a daylight saving time transition, you may get results that are adjusted by up to an hour. If you intend to work with the current day and want accurate elapsed times, then this should be expected. Otherwise, you'll want to fix the time to a particular date.
You aren't considering time ranges that cross midnight, for example 22:00 to 02:00 should be 4 hours (on most days). You should check if the values are in sequence, and add a day to the checkout value if not.

Answer 2

I did a short example in my Chrome console and got the correct answer with the following:
var start = moment('07:32', "HH:mm:ss")
var stop = moment('07:34', "HH:mm:ss")
var diff1 = moment.utc(stop).diff(moment(start))
start = moment("08:03", "HH:mm:ss")
stop = moment("08:33", "HH:mm:ss")
var diff2 = moment.utc(stop).diff(moment(start))
var total = moment(diff1)
total.add(diff2)
moment.utc(total).format("HH [ hour(s) and ] mm [ minute(s)]");
"00 hour(s) and 32 minute(s)"
So looks like your logic is correct without the arrays and for loops.

Answer 3

Friends... logic problems in my loops hehehheh
I was using
for (index = 0; index < checkins.length; ++index){
if (index <= checkouts.length) {
results.push(moment.utc(checkouts[index]).diff(moment(checkins[index])));
}
}
the correct is
for (index = 0; index < checkins.length; ++index){
if (index <= checkouts.length-1) {
results.push(moment.utc(checkouts[index]).diff(moment(checkins[index])));
}
}