The Intl.NumberFormat.supportedLocalesOf() method returns an array containing those of the provided locales that are supported in number formatting without having to fall back to the runtime's default locale.
The Intl.NumberFormat.prototype.format property returns a getter function that formats a number according to the locale and formatting options of this NumberFormat object.
The Intl.NumberFormat.prototype.resolvedOptions() method returns a new object with properties reflecting the locale and number formatting options computed during initialization of this NumberFormat object.