Values

JavaScript is dynamically typed: any value produced by a calculation has a type that can be Boolean, number, string, function, or object. However, variables do not have a type and can contain values of different types in succession (although this is not necessarily recommended). JavaScript values are said to be first-class citizens because there are no restrictions on their use: they can be stored in variables, arrays, objects, passed as function arguments, or returned as function results.

We distinguish between primitive types such as Boolean, number, character string, or symbols, and objects, which are basically associative tables. There are also predefined object types (classes), for example, Date , RegExp or Error There are also two singletons...