How to detect if a typescript function is async

Question

I write a function to handle exceptions thrown from async functions like:

protected safeAsync(f : e.RequestHandler) : e.RequestHandler {
    /* how to detect if `f` is an async function here ?? */
    const binded = f.bind(this);
    return async function innerCall(req : e.Request, res : e.Response, next : Function) {
        try {
            return await binded(req, res, next);
        } catch (err) {
            log.debug(err);
            return next(err);
        }
    }
}

The parameter f is supposed be an async function, such as

public async signupPost(req : e.Request, res : e.Response, next : Function) {/*...*/}

My question is:

In safeAsync, is there a way to detect if f is an async function, so I can log unexpected call to safeAsync ?

I believe it shouldn't matter if f has an async keyword or not. You should still be able to await it as long as it returns a promise. — David Sherret
– David Sherret, Commented Jan 30, 2016 at 16:02

Vadim Macagon · Accepted Answer · 2016-01-30 15:15:40Z

5

Since this is a runtime check the question you should be asking is whether or not JavaScript provides a way to check if a function is async. The answer is no, there is no fool proof way to tell if a function is async or not, it could even be both.

answered Jan 30, 2016 at 15:15

Vadim Macagon

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Lostfields · Accepted Answer · 2017-09-22 09:54:50Z

0

You can force it to be async just be doing Promise.resolve(f()), function "f" may return a promise or not but resolve will make it a promise anyway.

answered Sep 22, 2017 at 9:54

Lostfields

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