TypeScript Union Types

In TypeScript, we can define a variable which can have multiple type of values (i.e. number, string etc). This is called union type.

A union type allows us to define a variable with multiple types. This is achieved by using the pipe ('|') symbol between the types.

Union types helps in some situations; for example, when migrating from JavaScript code to TypeScript code.

1. Union Type Syntax

Use pipe symbol between multiple types which a variable should support.

 
let myVar: string | number;	//myVar can store string and number types

2. Union Type Example

Let’s see an example of typescript union types.

 
let myVar : string | number;		//Variable with union type declaration

myVar = 100;			//OK
myVar = 'Lokesh';		//OK

myVar = true;			//Error - boolean not allowed

Here, the myVar variable can hold both number and string, which allows us to have the flexibility to use both data types.

The TypeScript compiler makes sure that it alerts us if we try to assign a type of value that was not defined.

Drop me your questions in comments section.

Happy Learning !!