A character class matches any character in or not in a custom set of characters. When the v flag is enabled, it can also be used to match finite-length strings.

The spread (...) syntax allows an iterable, such as an array or string, to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected. In an object literal, the spread syntax enumerates the properties of an object and adds the key-value pairs to the object being created.

The optional chaining (?.) operator accesses an object's property or calls a function. If the object accessed or function called using this operator is undefined or null, the expression short circuits and evaluates to undefined instead of throwing an error.

The strict equality (===) operator checks whether its two operands are equal, returning a Boolean result. Unlike the equality operator, the strict equality operator always considers operands of different types to be different.

The async function declaration creates a binding of a new async function to a given name. The await keyword is permitted within the function body, enabling asynchronous, promise-based behavior to be written in a cleaner style and avoiding the need to explicitly configure promise chains.

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 multiplication assignment (*=) operator performs multiplication on the two operands and assigns the result to the left operand.

The limitingConeAngle attribute represents the angle in degrees between the spot light axis (i.e. the axis between the light source and the point to which it is pointing at) and the spot light cone. So it defines a limiting cone which restricts the region where the light is projected. No light is projected outside the cone.

The in operator returns true if the specified property is in the specified object or its prototype chain.

The increment (++) operator increments (adds one to) its operand and returns the value before or after the increment, depending on where the operator is placed.