Static initialization blocks are declared within a class. It contains statements to be evaluated during class initialization. This permits more flexible initialization logic than static properties, such as using try...catch or setting multiple fields from a single value. Initialization is performed in the context of the current class declaration, with access to private state, which allows the class to share information of its private properties with other classes or functions declared in the same scope (analogous to "friend" classes in C++).

The toLocaleDateString() method of Date instances returns a string with a language-sensitive representation of the date portion of this date in the local timezone. In implementations with Intl.DateTimeFormat API support, this method simply calls Intl.DateTimeFormat.

The SVG <style> element allows style sheets to be embedded directly within SVG content.

The isSupersetOf() method of Set instances takes a set and returns a boolean indicating if all elements of the given set are in this set.