“A value is an entity that takes on one of nine types. There are nine types (Undefined, Null, Boolean, String, Number, Object, Reference, List, and
Completion).”
1，Reference
The internal Reference type is not a language data type.
The Reference type is used to explain the behaviour of such operators as delete, typeof, and the assignment operators.Another use of the Reference type is to explain the determination of the this value for a function call.
2，List
The internal List type is not a language data type.
The List type is used to explain the evaluation of argument lists in new expressions and in function calls.
3，Completion
The internal Completion type is not a language data type.
The Completion type is used to explain the behaviour of statements (break, continue, return and throw) that perform nonlocal transfers of control.