The units-per-em attribute specifies the number of coordinate units on the "em square", an abstract square whose height is the intended distance between lines of type in the same type size. This is the size of the design grid on which glyphs are laid out.

The copyWithin() method of Array instances shallow copies part of this array to another location in the same array and returns this array without modifying its length.

The handler.apply() method is a trap for the [[Call]] object internal method, which is used by operations such as function calls.

The Reflect.apply() static method calls a target function with arguments as specified.

The Object.isExtensible() static method determines if an object is extensible (whether it can have new properties added to it).

The handler.isExtensible() method is a trap for the [[IsExtensible]] object internal method, which is used by operations such as Object.isExtensible().

The Reflect.isExtensible() static method is like Object.isExtensible(). It determines if an object is extensible (whether it can have new properties added to it).

The handler.deleteProperty() method is a trap for the [[Delete]] object internal method, which is used by operations such as the delete operator.

The unregister() method of FinalizationRegistry instances unregisters a target value from this FinalizationRegistry.

The register() method of FinalizationRegistry instances registers an value with this FinalizationRegistry so that if the value is garbage-collected, the registry's callback may get called.