Types

The Type System represents the different types of values supported by the language. The Type System checks the validity of the supplied values, before they are stored or manipulated by the program. This ensures that the code behaves as expected. The Type System further allows for richer code hinting and automated documentation too.

TypeScript provides data types as a part of its optional Type System. The data type classification is as given below −

The Any type

The any data type is the super type of all types in TypeScript. It denotes a dynamic type. Using the any type is equivalent to opting out of type checking for a variable.

Built-in types

The following table illustrates all the built-in types in TypeScript −

Data type	Keyword	Description
Number	number	Double precision 64-bit floating point values. It can be used to represent both, integers and fractions.
String	string	Represents a sequence of Unicode characters
Boolean	boolean	Represents logical values, true and false
Void	void	Used on function return types to represent non-returning functions
Null	null	Represents an intentional absence of an object value.
Undefined	undefined	Denotes value given to all uninitialized variables

Note − There is no integer type in TypeScript and JavaScript.

Null and undefined ─ Are they the same?

The null and the undefined datatypes are often a source of confusion. The null and undefined cannot be used to reference the data type of a variable. They can only be assigned as values to a variable.

However, null and undefined are not the same. A variable initialized with undefined means that the variable has no value or object assigned to it while null means that the variable has been set to an object whose value is undefined.

User-defined Types

User-defined types include Enumerations (enums), classes, interfaces, arrays, and tuple. These are discussed in detail in the later chapters.