Develop Reference

Moment js: moment(0) = Wed Dec 31 1969?

I tried to make null date.
so I tried to make them all 0 when I click the clear button.
this.clear = function () {
_this.newQuarters.forEach(function (_value, index) {
_value.startDate = 0;
_value.endDate = 0;
_value.suppressAllocation = false;
_value.quarters.forEach(function (_childValue, index) {
_childValue.startDate = 0;
_childValue.endDate = 0;
_childValue.suppressAllocation = false;
});
});
};
}
After that, I tried to add 0 at moment from other function.
this.newQuarters.forEach(function (_value, index) {
var startDate = moment(_value.startDate);
but, it display startDate = Wed Dec 31 1969.
Please help me to find to make all date are null.

When passing a number to the moment() function, it interpret it as a unix timestamp.
Which is the number of second since EPOCH time, or 01-01-1970.
So passing 0 to that function result in the very first second of jan 1 1970. As Bergi pointed out, you are probably displaying your dates in your local timezone, which could result in a time before 01-01-1970.
If you want to create a null date, you should set your startDate to null and handle it correctly ( with an if statement).
You could also set the date back to the current time by passing no argument to the moment() function.

Dates can be tricky to work with in an application. There is no such thing as time that is not time. At least not in the world of programming. For this reason we have to create our own understanding of what a lack of time will be.
There is no time without time but there is a lack of value.
You obviously understand this, you had an approach, in your case, you seem to be fine with simply having time be zero, it just broke when working with moment as moment is using EPOCH time. Thus, zero is time.
You are going to have to test like the rest of us.
this.newQuarters.forEach(function (_value, index) {
var startDate = _value.startDate ? moment(_value.startDate) : null;
Lack of time could be whatever you want, undefine, null, a beginning date
Be consistent: Database vendors and languages handle things differently, front end is not always the same time zone, etc.

If you are dealing with momentjs library, there is a function: invalid()
You can easily make your variables invalid moment object and control their validity.
let currentDate = moment(); // Valid moment object
console.log(currentDate.format());
// make the moment object invalid
currentDate = moment.invalid();
console.log(currentDate.isValid()); // Check validity
console.log(currentDate.format()); // Invalid date
// make the moment object valid again
currentDate = moment();
console.log(currentDate.isValid()); // Check validity
console.log(currentDate.format()); // A valid date
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>

Is there a way to watch times with moment.js and run a function when it does?

I'm new to moment.js and javascript and I couldn't seem to find anything in moment.js documentation or other questions here. I am comparing two different times, and would like to watch the time and run a function when Time A is equals to Time B.
so something like:
var a = TimeA
var b = TimeB
//watch the current time
when a === b {
//run a function
}
else {
//do nothing
}

There are many ways you can do this. But the most traditional way is to use an Interval Function as Badgy has pointed. Here is an working example for a 1 second interval:
var timeA = moment().add(10, 'seconds'); // 10 seconds from now
var tmr = setInterval(()=>{
var now = moment().unix();
var then = timeA.unix();
console.log(now, then)
if (now >= then) {
clearInterval(tmr);
console.log('Whatever you want to do');
}
}, 1000);
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.22.2/moment.min.js"></script>
I used .unix() method in moment.js because it returns the time in seconds. So it's better for comparison with the first time than a string like '2013-02-04T22:44:30.652Z' or the isSame() method because it uses milliseconds and can skip the exact moment. A second is a large enough time unit so it can be compared to the current time.

You could make a interval function and check every second if the times equal each other. Also throw a look at this it may help too.

How to get correct timestamp value in nodejs?

In my project my scheduling to post in social network sites using cron job,
timestamp value should end with zero instead of 1.
here is the node js code used:
var rule = new cron.RecurrenceRule();
rule.second = 0;
cron.scheduleJob(rule, function(){
var now = new Date();
var date = dateFormat(now, "dd-mm-yyyy, h:MM:ss TT");
console.log(Math.floor(new Date()/ 1000));
retrivepost(Math.floor(new Date()/ 1000).toString());
});
here is the timestamp value output log which i get in terminal
1517894101
1517894161
1517894221
1517894281
1517894341
1517894401
1517894461
1517894521
1517894581
1517894641
1517894701
1517894761
1517894821
1517894881
1517894941
1517895001
1517895061
1517895121

For me your code works just fine and logs timestamps ending with the zero second just like scheduled.
However, I think if your retrievepost() function depends on a timestamp being on the minute exactly you should round your date inside the .scheduleJob function to the nearest minute. A whole second later seems odd to me but imagine that you have some code just above that takes a while to compute. retrievepost() will fail then, even if you get it working right now.

Server-Side and Time-Specific script execution

I have a list of dates in an array(for now we can say that the dates are sorted). I want to have a script execute when the date matches a date in the array. My issue is figuring how to make this work on its own. I would like to have a server somehow act like an alarm clock that can run a script for a scheduled date and time. If anyone could help with suggestions to make this work I would appreciate it.
set date >>> if (currentDate == set date) >>> run script for the respective data
Please ask if you need clarification.

The way to do this with parse is a class with a date attribute. Create one object per date in your array of dates (they needn't be sorted).
Create a scheduled job that upon running, query's the class for the first date equal to the current date. If one is found, do whatever you want to do when an alarm is triggered.
So, something like...
Parse.Cloud.job("checkStatus", function(request, status) {
var today = new Date();
today.setHours(0, 0, 0, 0);
var tomorrow = new Date(today);
tomorrow.setDate(tomorrow.getDate() + 1);
var query = new Parse.Query("MyAlarmClass");
query.greaterThanOrEqualTo('theDateAttribute', today);
query.lessThan('theDateAttribute', tomorrow);
return query.first().then(function(anAlarm) {
if (anAlarm) {
// do whatever should be done on the alarm
} else {
// do nothing
}
}).then(function() {
status.success();
}, function(error) {
status.error(JSON.stringify(error));
});
});
Schedule this to run at least twice per day (or faster than whatever resolution you need on the alarms).

Add a duration to a moment (moment.js)

Moment version: 2.0.0
After reading the docs, I thought this would be straight-forward (Chrome console):
var timestring1 = "2013-05-09T00:00:00Z";
var timestring2 = "2013-05-09T02:00:00Z";
var startdate = moment(timestring1);
var expected_enddate = moment(timestring2);
var returned_endate = startdate.add(moment.duration(2, 'hours'));
returned_endate == expected_enddate // false
returned_endate // Moment {_i: "2013-05-09T00:00:00Z", _f: "YYYY-MM-DDTHH:mm:ss Z", _l: undefined, _isUTC: false, _a: Array[7]…}
This is a trivial example, but I can't even get it to work. I feel like I'm missing something big here, but I really don't get it. Even this this doesn't seem to work:
startdate.add(2, 'hours')
// Moment {_i: "2013-05-09T00:00:00Z", _f: "YYYY-MM-DDTHH:mm:ss Z", _l: undefined, _isUTC: false, _a: Array[7]…}
Any help would be much appreciated.
Edit:
My end goal is to make an binary status chart like the one I'm working on here:
http://bl.ocks.org/phobson/5872894
As you can see, I'm currently using dummy x-values while I work through this issue.

I think you missed a key point in the documentation for .add()
Mutates the original moment by adding time.
You appear to be treating it as a function that returns the immutable result. Easy mistake to make. :)
If you use the return value, it is the same actual object as the one you started with. It's just returned as a convenience for method chaining.
You can work around this behavior by cloning the moment, as described here.
Also, you cannot just use == to test. You could format each moment to the same output and compare those, or you could just use the .isSame() method.
Your code is now:
var timestring1 = "2013-05-09T00:00:00Z";
var timestring2 = "2013-05-09T02:00:00Z";
var startdate = moment(timestring1);
var expected_enddate = moment(timestring2);
var returned_endate = moment(startdate).add(2, 'hours'); // see the cloning?
returned_endate.isSame(expected_enddate) // true

I am working on an application in which we track live route. Passenger wants to show current position of driver and the expected arrival time to reach at his/her location. So I need to add some duration into current time.
So I found the below mentioned way to do the same.
We can add any duration(hour,minutes and seconds) in our current time by moment:
var travelTime = moment().add(642, 'seconds').format('hh:mm A');// it will add 642 seconds in the current time and will give time in 03:35 PM format
var travelTime = moment().add(11, 'minutes').format('hh:mm A');// it will add 11 mins in the current time and will give time in 03:35 PM format; can use m or minutes
var travelTime = moment().add(2, 'hours').format('hh:mm A');// it will add 2 hours in the current time and will give time in 03:35 PM format
It fulfills my requirement. May be it can help you.

For people having a startTime (like 12h:30:30) and a duration (value in minutes like 120), you can guess the endTime like so:
const startTime = '12:30:00';
const durationInMinutes = '120';
const endTime = moment(startTime, 'HH:mm:ss').add(durationInMinutes, 'minutes').format('HH:mm');
// endTime is equal to "14:30"