Serializing datetime.date to JSON with javascript Date [duplicate]

Question

How can I serialize a python list contains datetime.date objects, to a JSON array of javascript Date objects? For example:

lst = [datetime.date(2013, 12, 30), datetime.date(2013, 12, 31)]
print serialize(lst)
# should print "[new Date(2013, 12, 30), new Date(2013, 12, 31)]"

I've tried json.dumps with a custom handler but the handler can only return serializable objects and not the actual JSON syntax.

You can't have "...a JSON array of JavaScript Date objects." You can have a JSON array, or you can have a JavaScript array containing Date objects. JSON != JavaScript, and JSON doesn't have any concept of dates. — T.J. Crowder
– T.J. Crowder, Commented Dec 30, 2013 at 15:15
@T.J.Crowder thanks for the clarification, so how can I have a javascript array with Date objects? — Tzach
– Tzach, Commented Dec 30, 2013 at 15:19
basically, use .isoformat(). Date type is not supported in JSON. — zs2020
– zs2020, Commented Dec 30, 2013 at 15:19
@zsong thanks. It's not critical that the array will be JSON, javascript is ok as well. If i use .isoformat I will have to do another pass on the array in javascript to convert the values to Date objects and that's something I prefer not to do. — Tzach
– Tzach, Commented Dec 30, 2013 at 15:22
Watch out - when you use new Date(...) in JavaScript, the months range 0-11. In python they are 1-12. — Matt Johnson-Pint
– Matt Johnson-Pint, Commented Dec 30, 2013 at 17:38

Explosion Pills · Accepted Answer · 2013-12-30 15:22:42Z

0

JavaScript Date objects are json-serialized to strings. However, you can construct a date object from this serialized string. The closest string that the python datetime.date class provides seems to be isoformat.

lst = [datetime.date(2013, 12, 30).isoformat(),
    datetime.date(2013, 12, 31).isoformat()]

On the JavaScript side, these will simply be strings like "2013-12-31". You can construct a date object from that -- new Date("2013-12-30"). It will probably look something like:

lst = JSON.parse(lstJson);
lst.forEach(function (date) {
    var date = new Date(date);
});

answered Dec 30, 2013 at 15:22

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3 Comments

Tzach Over a year ago

Thanks, but is there a way to do all of that directly in python?

Explosion Pills Over a year ago

@Tzach do what? You can't store JavaScript date objects themselves in JSON. They are serialized to the representative strings.

Tzach Over a year ago

I doesn't really matter if the array is JSON or javascript, all I need is an output string that looks like the one in the question, so I can embed it into an existing JS code, without iterating over the array in JS.

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