Typescript Note: ReturnType
I recently need to define the return type of function. But the return type I assigned doesn't seem to work. After looking into the type definition I realize that the required return type was incomplete.
Fortunately I learned about Type Inference and ReturnType in TypeScript.
An example for using ReturnType
for infering return type is like this:
const parseData = (datum: string) => {
return parseInt(datum, 10)
}
type A = ReturnType<typeof parseInt>
- The
typeof
will return the type of the function, which is(datum: string) => number
. - Then the
RetunType
will capture the return type - The result is type A which is
number