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 Object.freeze() method freezes an object: that is, prevents new properties from being added to it; prevents existing properties from being removed; and prevents existing properties, or their enumerability, configurability, or writability, from being changed. In essence the object is made effectively immutable. The method returns the object being frozen.
The Object.getNotifer() method was used to create an object that allows to synthetically trigger a change, but has been deprecated and removed in browsers.
The Object.getOwnPropertyDescriptor() method returns a property descriptor for an own property (that is, one directly present on an object and not in the object's prototype chain) of a given object.
The Object.observe() method was used for asynchronously observing the changes to an object. It provided a stream of changes in the order in which they occur. However, this API has been deprecated and removed from browsers. You can use the more general Proxy object instead.
The toLocaleString() method returns a string representing the object. This method is meant to be overridden by derived objects for locale-specific purposes.
The Object.unobserve() method was used to remove observers set by Object.observe(), but has been deprecated and removed from Browsers. You can use the more general Proxy object instead.