TypeScript Type Aliases

TypeScript provides a powerful way to define custom types using type aliases. Type aliases allow you to create a new name for a type, which can be a primitive, union, intersection, tuple, or any other valid TypeScript type. This can make your code more readable and maintainable.

Defining a Type Alias

To define a type alias, use the type keyword followed by the alias name and the type definition:

type StringAlias = string;
type NumberAlias = number;
type BooleanAlias = boolean;

Using type aliases

Once you have defined a type alias, you can use it to declare variables, function parameters, return types, and more:

type UserID = string;
let UserId: UserID = "abcd12345";

Complex Type Aliases

Type aliases can also be used to define more complex types such as unions, intersections, tuples, and generics:

Object Type Alias

type User = {
    id: number;
    name: string;
    email: string;
}
 
let user: User = {
    id: 1,
    name: "Pratap Das",
    email: "pratap.das@gmail.com"
}

Union Type Alias

type Status = "active" | "inactive" | "pending";
 
let currentStatus: Status = "active";
 
// or
type Status = "success" | "error" | "loading";
 
let currentStatus: Status = "loading";

Intersection Type Alias

type Person = {
    name: string;
}
type Employee = {
    employeeId: number;
    department: string;
}
let employee: Person & Employee = {
    name: "Prata Das",
    id: 999,
    department: "Engineering"
}

Tuple Type Alias

type Point = [number, number];
let point: Point = [10, 20];

Advantages of Type Aliases

• Readability: Type aliases make your code more readable by giving meaningful names to types.
• Maintainability: Type aliases help in maintaining consistency across your codebase by defining types in a single place.
• Reusability: Type aliases can be reused across multiple parts of your codebase, reducing duplication.

Type aliases are a versatile feature in TypeScript that can help you write cleaner and more maintainable code. Use them to simplify your type definitions and improve the readability of your code.