Casting to Change Type
In this lesson, you will see how to move from one type to another.
We'll cover the following...
How do we cast? #
TypeScript can cast using two different forms: <> or as. The former is not recommended because it conflicts with the JSX/TSX format which is now becoming popular because of React. The latter is just as good, and it works in all situations.
The first way is to use the symbols < and > with the type desired in between. This syntax requires the cast before the variable that you want to coerce.
The second way is to use the keyword as. as is placed after the variable you want to cast and followed by the type you want to cast.
The following code demonstrates an unknown type cast to a number.
const unknownType: unknown = "123"const cast1: number = <number>unknownType;const cast2: number = unknownType as number;
Casting constraints
If you try to cast to a string directly without using an unknown type, TypeScript will warn that there are not sufficient overlaps. The TypeScript transpiler gives the solution: casting to ...