How do I format a date as ISO 8601 in moment.js?

moment().toISOString(); // or format() - see below

http://momentjs.com/docs/#/displaying/as-iso-string/

Update Based on the answer: by @sennet and the comment by @dvlsg (see Fiddle) it should be noted that there is a difference between format and toISOString. Both are correct but the underlying process differs. toISOString converts to a Date object, sets to UTC then uses the native Date prototype function to output ISO8601 in UTC with milliseconds (YYYY-MM-DD[T]HH:mm:ss.SSS[Z]). On the other hand, format uses the default format (YYYY-MM-DDTHH:mm:ssZ) without milliseconds and maintains the timezone offset.

I've opened an issue as I think it can lead to unexpected results.

Also possible with vanilla JS

new Date().toISOString() // "2017-08-26T16:31:02.349Z"

Use format with no parameters:

var date = moment();
date.format(); // "2014-09-08T08:02:17-05:00"

(http://jsfiddle.net/8gvhL1dz/)