discourse/app/assets/javascripts/locales/ar.js.erb

//= depend_on 'client.ar.yml'
//= require locales/i18n
<%= JsLocaleHelper.output_locale(:ar) %>

// original moment.js implementation can be found here:
// https://github.com/moment/moment/blob/b7ec8e2ec068e03de4f832f28362675bb9e02261/locale/ar.js#L185-L191
moment.updateLocale("ar", {
  postformat(string) {
    return string;
  }
});