To clear up some doubts about moment.js - javascript

I got stuck in my project, due to some doubts related to moment.js. I'll state some conclusions here I made during writing backend on project, and please can someone correct me if something is wrong?
For example, if I get datetime string from fronted, in format:
"THU 18 MAR 2017 09:20 AM", I should create moment object passing this string to it and corresponding token "ddd DD MMM YYYY HH:mm A" as passed string is not in standard ISO 8601 format.
var datetime = moment(datetimeFromFrontend, "ddd DD MMM YYYY HH:mm A");
Now I have moment object that can be formated in way I want, calling format() function on moment object.
If I want to do some manipulations with datetime generally (for example, compare to today's datetime, or compare only time part), is it mandatory to convert all manipulating datetimes, times or whatever to moment object with same format and using isBefore, isEqual and so on, or can I somehow compare them using >, <, <=, =< ?
If I need to compare (>, < etc) datetime or just time part with value retrieved from SQL database (which is DATETIME or TIME data type), should I pass both comparing values to moment object, convert them in same format and then do manipulations?
And how to save to SQL database column which is DATETIME, or TIME type? Should do some transforms from moment object to string using format()? SQL will automatically convert passing string to corresponding data type?
Example:
var now = moment();
I assume that "now" can't be passed to sql query directly as it is moment object, it should be converted to string (and rely on SQL automatic conversion from string/nvarchar to datetime) or should I save it as moment().toDate() ?

If I need to compare (>, < etc) datetime or just time part with value retrieved from SQL database (which is DATETIME or TIME data type), should I pass both comparing values to moment object, convert them in same format and then do manipulations?
You might want to lookup the docs for that
You have Query functions that can compare moments and even Date objects, for example, this is the entry for the .after function
moment().isAfter(Moment|String|Number|Date|Array);
as you can see, you can pass anything to .isAfter and it will do that job for you
moment().isAfter(new Date(2017, 2, 4))
// true
moment(new Date(2016, 2, 4)).isAfter(new Date(2017, 2, 4))
// false
Of course the easiest way to compare >, < or === is to get the timestamp using Date::getTime, but that's ugly code
And how to save to SQL database column which is DATETIME, or TIME type? Should do some transforms from moment object to string using format()? SQL will automatically convert passing string to corresponding data type?
I think it depends how you SQL works and how your server communicates to it, ORACLE, you should refer to any documentation about storing date objects inside your sql, eventually dates and formats are all about making unix-timestamps human readable/understandable.
I assume that "now" can't be passed to sql query directly as it is moment object, it should be converted to string (and rely on SQL automatic conversion from string/nvarchar to datetime) or should I save it as moment().toDate() ?
Ask yourself what kind of benefits you or anyone that may use you API will gain from getting agnostic Date objects from your DB rather then just plain strictly formatted strings?

Related

Parse JSON DateTime object to local time in JQuery by ignoring timezone

I am facing an issue while parsing JSON Date Time object using moment(of course I tried many approaches suggested in Stackoverflow but nothing worked in my case).
In my application, I'm storing a DateTime value as UTC DateTime. Now when I'm displaying I need to display it according to the browser timezone. After going through many StackOverflow questions, I used "moment.js" as below
//From server, the Date object looks like /Date(1506510057813)/
//The equivalent DateTime value stored in Database is 2017-09-27 13:00:57.813
fuction DateTimeFormatter(value)
{
if (value != undefined) {
var newValue = new Date(moment.utc(value));
//But at this line, even with just moment(value) all I am getting is DateTime which is not same as UTC time.
//I don't want any time zone to get appended all I want is just 13:00:57
var newHours = newValue.getHours() - newValue.getTimezoneOffset() / 60;
var newMinutes = (newHours + '.0').split('.')[1] * 6;
newValue.setHours(newHours);
newValue.setMinutes(newMinutes);
return moment(newValue).format(applicationTableDateFormat);
}
else
return "";
}
Please let me know what I am doing wrong or is there any other way I can display time as per browser time zone.
Once you have a UTC moment, you can convert it to local.
moment.utc(value).local().format(...)
https://momentjs.com/docs/#/manipulating/local/
But it sounds like maybe your real problem is when you store the date. If you're storing it as UTC, make sure you actually convert the local value to UTC before you store it. That way when you read it, you get a predictable value that you can safely convert to any locale.
Angularjs has its own mechanism to display formatted dates on views you just needs an absolute representation of a date and it takes care of the rest. And by absolute, I mean, a Date which is settled in a timezone whether it's utc or not, you need to know what timezone you are talking about.
The date filter
It's a filter from the core module of angularjs and it accepts:
"... either as Date object, milliseconds (string or number) or various ISO 8601 datetime string formats (e.g. yyyy-MM-ddTHH:mm:ss.sssZ and its shorter versions like yyyy-MM-ddTHH:mmZ, yyyy-MM-dd or yyyyMMddTHHmmssZ). If no timezone is specified in the string input, the time is considered to be in the local timezone." (Angularjs date filter)
The problem
Angularjs need a proper date input in order to display it correctly, in your case you seem to have the milliseconds format (sort of, /Date(1506510057813)/), you could use that and extract the numeric part and input that on the pipe, or you can change the server to send the ISO 8601 date (a.k.a., yyyy-MM-ddTHH:mm:ss.sssZ).
For example:
let rawDate = '/Date(1506510057813)/';
let re = /\/Date\((\d+)\)\//g; // regex to extract number from the string date
let myDate = new Date(Number(re.exec()[1])) // extract the milliseconds
Or
let rawDate = '2017-09-27T11:00:57.813Z';
let myDate = new Date(rawDate)// and you don't need to do anything else
Either way you'd end up with something like this:
<span> {{ myDate | date }}</span>

Convert string to new Date object in UTC timeZONE

Can anyone let me know how to convert a string to a date Object with UTC time zone in ExtJs?
String is "2015-10-07T23:59:00". I would like to get the same in Date Object without changing the timezone.
First of all, your date string does not have a timezone.
When you make a JavaScript date object from a string, there are two possible outcomes you could expect:
You may want the date to be 23:59 Local (23:59 CEST in my case).
In this case, you want to use new Date("2015-10-07 23:59:00") with plain javascript (note the missing T), or Ext.Date.parse("2015-10-07T23:59:00","c");.
You may want the date to be 23:59 UTC (e.g. 01:59 CEST).
In this case, you want to use new Date("2015-10-07T23:59:00").
Of course, whenever you output the date, you have to get the date in the correct time zone as well. The console/toString will usually show it in local time. JavaScript does provide getUTC... methods if you require other time zones.
You see, using Time Zones with JavaScript is a painful experience. I would recommend to try moment.js if you need full time zone support.
You can use Ext.Date.parse.It gives Date Object as output.It syntax is:
Ext.Date.parse( String input, String format, [Boolean strict] )
For Example:
Ext.Date.parse("2015-10-07T23:59:00", "Y-m-dTH:i:s");
try
var millisFromEpoch = Date.parse('2015-10-07T23:59:00');
it will parse date in GMT timezone, Ext.date.parse use the current timezone instead

How to work with datetimes betwixt javascript, JSON, and python, and mongodb?

Colleague and I have scabbed together a little app that uses a bunch of JS in the browser, and communicates with a Tornado (Python3) server via JSON, the server uses mongodb as a backing store for persistent data. This is a sort of first for both of us.
What we're finding difficult is how to interchange datetime information between the JS and Python. We do believe that we should use UTC times for everything. JSON doesn't have a datetime literal, so we have to encode it somehow. We naively (?) used the JS notion of milliseconds from 1970 and have been sharing big integers back and forth. So the JS code might get the current utc now time with something like:
var newTime = new Date().getTime();
On the Python3/mongo side, we'd like to use real datetime objects, so we convert that with something like:
datetime.datetime.utcfromtimestamp(jsMilliseconds / 1000)
But then when we have to send date back, said Python3 object only has a timestamp() method. And round tripping that doesn't seem to create the same time. So we've been frustrated with this.
What we're looking for is for someone with experience to give us a good set of idioms to use here. Should we be using strings, instead of the ms integers when passing back and forth with JSON? What are the recommended methods to use on both sides to go between that format? Or should we stick with the integers and which methods should we be using then?
There are obviously a lot of requirements to consider when dealing with time. However, in the case you want to maintain a Date/Time to be displayed to user in their time zone and use mongo/python/java/javascript, I've used ISO 8601 date formats and always store UTC (Zulu) time. Also, if you truly want to maintain the actual time that something occured, not only do you need to store the "date/time" you need to also store the "timezone" (for example IANA timezone string) where the event occurred.
For a lifetime a reading, you can search for "date time best practices". This answer has a good start on discussion: Daylight saving time and time zone best practices
Alright, now to the code (all of this can be found readily on the internet if you search for
" parse||output ISO 8601 parsing" (e.g. "python parse ISO 8601 date string"):
JSON - on the wire between JavaScript and Python backend send a complex (can be simple if you have no need to preserve time zone) object with ISO-8601 formatted string and string to store time zone string:
{
"dateTime": "1970-07-10T12:00:00.047Z",
"timeZone": "America/New_York"
}
Java Script
a. read datetime string JavaScript: Which browsers support parsing of ISO-8601 Date String with Date.parse
var d = Date.parse("2011-04-26T13:16:50Z");
b. write datetime string How do I output an ISO 8601 formatted string in JavaScript?
var date = new Date();
date.toISOString(); //"2011-12-19T15:28:46.493Z"
Python
a. read datetime string How do I translate a ISO 8601 datetime string into a Python datetime object?
import dateutil.parser
yourdate = dateutil.parser.parse(datestring)
b. write datetime string Python - Convert date to ISO 8601
import dateutil.parser as parser
date.isoformat()
Mongo - store datetime as native datetime field http://docs.mongodb.org/manual/reference/mongodb-extended-json/#date
a. store datetime string (notice "$date" and that datetime is in ZULU/UTC (denoted by 'Z')):
"dateTime" : { "$date" : "1970-07-10T13:00:00.047Z"}
Reference:
1. IANA TimeZone Databasehttp://en.wikipedia.org/wiki/Tz_database
2. The google calendar API (event resource) can be used as an example for RFC 3339, as well (see start/end): https://developers.google.com/google-apps/calendar/v3/reference/events

Compare ISO date without time stamp in javascript

I am querying data using OData, url looks like http://myurl.com/api/Customer?$filter=ResDate eq DateTime'2014-03-15T12:01:55.123'.
I'm getting date/time from jquery.datepicker instead of the static date and using moment.js to convert from DD-MM-YYYY to YYYY-MM-DDTHH:mm:ss in order to pass it to web service.
function convertDateToISOdate(date){
var newDate = moment(date,'DD-MM-YYYY').format('YYYY-MM-DDTHH:mm:ss');
return newDate;
}
Date returns from the function, is 2014-03-15T00:00:00.
Problem : 2014-03-15T12:01:55.123 is not equal to 2014-03-15T00:00:00, so there's no record selected.
What I want is , just to compare the date , not include time stamp.
Note : I can not change the format date/time at server side(Web service) because it's not belongs to me.
Any idea is much appreciated.
Your first call to moment(date,'DD-M-YYYY') is stripping the time information from the incoming data. try using moment(date) (no format) instead because momentjs recognizes your incoming date format intrinsically, without having to be told which format to use, and will correctly parse the H:M:S data, too.
MomentJS date parse information

Passing datetime with http request

I need to pass a date time (in 2012-09-23 21:00:00 format generated by dropdown boxes and converted to that format with javascript (client side that is)) with GET method to a php file which then gets mysql records sorted by that time.
What is the best way of passing this date?
The options I consider are:
making separate get parameters for each piece of info (e.g ?startYear=2012&startMonth=09&startDay=23&startHour=....)
this could work, but what if I add more different filters. It will be too busy there. Or it's not an issue?
Passing timestamp. I consider this to be the best option. However when I convert the date to timestamp it gives me incorrect result. The function will be below.
Passing in 2012-09-23 21:00:00 format by pre-processing with encodeURIComponent
Any suggestions?
Date to timestamp conversion (related to point 2):
function getTimestamp(str) {
var d = str.match(/\d+/g); // extract date parts
return +new Date(d[0], d[1] - 1, d[2], d[3], d[4], d[5]); // build Date object
}

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