JavaScript has a number formatter (part of the Internationalization API).
// Create our number formatter.
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
// These options are needed to round to whole numbers if that's what you want.
//minimumFractionDigits: 0, // (this suffices for whole numbers, but will print 2500.10 as $2,500.1)
//maximumFractionDigits: 0, // (causes 2500.99 to be printed as $2,501)
});
formatter.format(2500); /* $2,500.00 */
Use undefined
in place of the first argument ('en-US'
in the example) to use the system locale (the user locale in case the code is running in a browser). Further explanation of the locale code.
Here's a list of the currency codes.
Intl.NumberFormat vs Number.prototype.toLocaleString
A final note comparing this to the older .toLocaleString
. They both offer essentially the same functionality. However, toLocaleString in its older incarnations (pre-Intl) does not actually support locales: it uses the system locale. So when debugging old browsers, be sure that you're using the correct version (MDN suggests to check for the existence of Intl
). There isn't any need to worry about this at all if you don't care about old browsers or just use the shim.
Also, the performance of both is the same for a single item, but if you have a lot of numbers to format, using Intl.NumberFormat
is ~70 times faster. Therefore, it's usually best to use Intl.NumberFormat
and instantiate only once per page load. Anyway, here's the equivalent usage of toLocaleString
:
(2500).toLocaleString('en-US', {
style: 'currency',
currency: 'USD',
}); /* $2,500.00 */
Some notes on browser support and Node.js
- Browser support is no longer an issue nowadays with 98% support globally, 99% in the US and 99+% in the EU
- There is a shim to support it on fossilized browsers (like Internet Explorer 8), should you really need to
- Node.js before v13 only supports
en-US
out of the box. One solution is to install full-icu, see here for more information
- Have a look at CanIUse for more information
eval()
is not necessary. This will work fine:
var date = new Date(parseInt(jsonDate.substr(6)));
The substr()
function takes out the /Date(
part, and the parseInt()
function gets the integer and ignores the )/
at the end. The resulting number is passed into the Date
constructor.
I have intentionally left out the radix (the 2nd argument to parseInt
); see my comment below.
Also, I completely agree with Rory's comment: ISO-8601 dates are preferred over this old format - so this format generally shouldn't be used for new development.
For ISO-8601 formatted JSON dates, just pass the string into the Date
constructor:
var date = new Date(jsonDate); //no ugly parsing needed; full timezone support
Best Answer
Just to expand on casperOne's answer.
The JSON spec does not account for Date values. MS had to make a call, and the path they chose was to exploit a little trick in the javascript representation of strings: the string literal "/" is the same as "\/", and a string literal will never get serialized to "\/" (even "\/" must be mapped to "\\/").
See http://msdn.microsoft.com/en-us/library/bb299886.aspx#intro_to_json_topic2 for a better explanation (scroll down to "From JavaScript Literals to JSON")
A solution would be to just parse it out:
However I've heard that there is a setting somewhere to get the serializer to output
DateTime
objects with thenew Date(xxx)
syntax. I'll try to dig that out.The second parameter of
JSON.parse()
accepts areviver
function where prescribes how the value originally produced by, before being returned.Here is an example for date:
See the docs of JSON.parse()