Format Date in Javascript

Question

How to format this:

/Date(1292962456255)/

as regular looking date in JavaScript/jQuery?

• Pekka: What kind of a date is this? A timestamp?
• slandau: Comes back to Json like this from a c3 Datetime object
• KJYe.Name: what exactly is the expected output of this date?
• slandau: I really don't know. For some reason passing a c# datetime through json to the view comes back like this after I perform a .toString() on it
• slandau: @John -- maybe? i really dont know

Answer 1

This is what I call an "Microsoft Date" and the following function will convert the encoded date to a javascript date time

 var msDateToJSDate = function(msDate) {
 var dtE = /^\/Date\((-?[0-9]+)\)\/$/.exec(msDate);
 if (dtE) {
 var dt = new Date(parseInt(dtE[1], 10));
 return dt;
 }
 return null;
 }

• Theo: This isn't valid JavaScript, there should be a = instead of a : on the first line -- and what's with the return msEncodedDate? If the string doesn't match the pattern, return the function itself? That doesn't make any sense at all.
• John Hartsock: @Theo your right about the equal. but your second observation is wrong. The function will return the a JS date if the string matches the regex. otherwise return back the original value passed in. Clearly you could modify this to return an error code or null.
• Theo: Ah, sorry, I misread and took the argument name for the function name. It's still a strange thing to do, I would be very surprised to get a string back when I expect a date. Returning null or raising an exception would be much more appropriate.
• John Hartsock: @Theo I would hope that C# is not passing invalid dates through JSON
• Theo: You can never trust that what you get will always be correct.

Answer 2

Check out moment.js! It's "A lightweight javascript date library for parsing, manipulating, and formatting dates". It is a really powerful little library.

Here's an example...

var today = moment(new Date());
today.format("MMMM D, YYYY h:m A"); // outputs "April 11, 2012 2:32 PM"
// in one line...
moment().format("MMMM D, YYYY h:m A"); // outputs "April 11, 2012 2:32 PM"

Here's another example...

var a = moment([2012, 2, 12, 15, 25, 50, 125]);
a.format("dddd, MMMM Do YYYY, h:mm:ss a"); // "Monday, March 12th 2012, 3:25:50 pm"
a.format("ddd, hA"); // "Mon, 3PM"
a.format("D/M/YYYY"); // "12/3/2012"

---

Also, its worth mentioning to checkout date.js. I think the two libraries complement each other.

Answer 3

The number is a timestamp with millisecond resolution. This number can be passed to JavaScript's Date class' constructor. All that is needed is some code to extract it from the string:

var dateString = "/Date(1292962456255)/";
var matches = dateString.match(/^\/Date\((\d+)\)\/$/);
var date = new Date(parseInt(matches[1], 10));

The regexp on the second line gets a bit messy since the string contains /, ( and ) at precisely the positions that they are needed in the regexp (are you sure what you have is strings that look like that, and not a description of a pattern that would extract them?).

Another way of doing it is to use eval:

var dateString = "/Date(1292962456255)/";
var date = eval("new " + dateString.substring(1, dateString.length - 1));

but that may open up for an XSS attack, so I don't recommend it.

• John Hartsock: Dont forget the radix on parseInt
• Theo: Radix is not needed since it defaults to base 10.
• John Hartsock: that is not actually correct. Radix does not default to base 10. "If no radix argument is provided or if it is assigned a value of 0, the function tries to determine the base. If the string starts with a 1-9, it will be parsed as base 10. If the string starts with 0x or 0X it will be parsed as a hexidecimal number. If the string starts with a 0 it will be parsed as an octal number. (Note that just because a number starts with a zero, it does not mean that it is really octal.) "

Answer 4

I think this a microtime. Similar to PHP's microtime function. Or in new Date().getTime() in JavaScript.

// PHP
$ php -r "var_dump(microtime(true));"
float(1292963152.1249)
// JavaScript
new Date().getTime()
1292963411830

• Theo: He asked for code that would format the date in the string, not what it was.