By Microsoft Team

 

Summary: in this tutorial, you will learn how to define new names for types using type aliases. 

 

Introduction to TypeScript type aliases 

 

Type aliases allow you to create a new name for an existing type. The following shows the syntax of the type alias:

 

type alias = existingType;

 

The existing type can be any valid TypeScript type. 

 

The following example use the type alias chars for the string type:

 

type chars = string;
let messsage: chars; // same as string type

 

It’s useful to create type aliases for union types. For example:

 

type alphanumeric = string | number;
let input: alphanumeric;
input = 100; // valid
input = 'Hi'; // valid
input = false; // Compiler error

 

Summary 

 

  • Use type aliases to define new names for existing types.