The entries() method of Set instances returns a new set iterator object that contains an array of [value, value] for each element in this set, in insertion order. For Set objects there is no key like in Map objects. However, to keep the API similar to the Map object, each entry has the same value for its key and value here, so that an array [value, value] is returned.

The delete() method of Set instances removes a specified value from this set, if it is in the set.

The union() method of Set instances takes a set and returns a new set containing elements which are in either or both of this set and the given set.

The difference() method of Set instances takes a set and returns a new set containing elements in this set but not in the given set.

The keys() method of Set instances is an alias for the values() method.

The isDisjointFrom() method of Set instances takes a set and returns a boolean indicating if this set has no elements in common with the given set.

The Atomics.load() static method returns a value at a given position in the array.

The unary negation (-) operator precedes its operand and negates it.

The JavaScript exception "missing : after property id" occurs when objects are created using the object initializer syntax. A colon (:) separates keys and values for the object's properties. Somehow, this colon is missing or misplaced.

The JavaScript exception "functions cannot be labelled" occurs when a function declaration has a label before it.