Transform an unidentified function into a new type using TypeScript

Consider the following code snippet:

type T = (x: number) => boolean;

let fn = function(a: string, b: boolean, c: T){};

fn('yes', true, ()=> {

});

Unfortunately, this code will not compile. The goal is to cast the anonymous function to a specific type like this:

fn('yes', true, ()=> {

} as T);

Alternatively, you may attempt to do it like this:

fn('yes', true, <T>()=> {

});

However, attempting these methods results in an error message:

Cannot find name "as"

Is there a way to cast the function to another type directly within the code?

Answer №1

After some experimentation, I discovered that the following syntax is what actually works:

type T = (x: number) => boolean;

let fn = function(a: string, b: boolean, c: T){};

fn('yes', true, (() => {

}) as any);

fn('yes', true, <any>(() => {

}));

It seems to require more parentheses than I initially anticipated.

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