TS Basic: Type Assertion

August 10, 2023

Sometimes you will have information about the type of value that TS can’t know about. Type assertions are used to explicitly specify the type of a value when the TS compiler is unable to infer it automatically.

Two ways to perform type assertion

1. Angle Bracket Syntax <>

• older form of type assertion
• you use brackets <> to specify the target type

let someValue: any = 'Hello';
let strLength: number = (<string>someValue).length

2. “as” syntax

• newer form of assertion
• use the as keyword to specify the target

let someValue: any = 'Hello';
let strLength: number = (someValue as string).length

👌They are simply a way to provide hints to the TS compiler for type checking during the compilation process