How do can I add a new format option to Moment.js locales?

Question

I want to be able to format a date as the day and the shortened month. (ex: 20 Sep for en-gb, Sep 20 for en). However, the closest localized format that Moment.js has us the format 'll' which is Sep 20, 2017 for en. I want to be able to create a new format that excludes the year from 'll'. How can I best achieve this?

The end result I want (assuming today is Sept 20):

moment.locale('en');
moment().format('my-new-format')  ---> Sep 20
moment.locale('en-gb');
moment().format('my-new-format')  ---> 20 Sep
moment().format('ll')             ---> 20 Sep, 2017

Answer 1

That seems to work with me... :

moment.updateLocale("en", { longDateFormat : { "[my-new-format]" : "MMM D" } });
moment.updateLocale("en-gb", { longDateFormat : { "[my-new-format]" : "DD MMM" } });

And then

moment.locale('en');
moment().format('[my-new-format]');

So you don't overwrite existing formats.