Node measure execution time - return value from an async passed as parameter to another function

Question

I want to write a function to measure the performance of parts of code (other methods) that could return a value. This is what I came out at the moment:

const fn = async (): Promise<any> => {
    setTimeout(async (): Promise<any> => {
        return new Promise((resolve) => resolve('Hello World!'));
    }, 3000);
};

async measure(fn: () => Promise<any>): Promise<any> {
    const startTime = this.performance.now();
    const result = await functionToMeasure();
    const endTime = this.performance.now();

    const executionTime = endTime - startTime;
    console.log(`Executed in ${executionTime} ms`);

    return result;
}

const result = async measure(functionToMeasure); // result is undefined

The result is that functionToMeasure actually runs but it never returns something and at the moment I can use it only with void function.

I'd like to fix it if possible, or I can change completely if there's a better way to do it.

EDIT:

Actual code

const callback = async (): Promise<any> => {
    return await doSomethingAndReturn();
};
const searchResults: string[] = await measure(callback);

Do I've to wrap doSomethingAndReturn in an async Promise?

You should be wrapping the setTimeout in the Promise's executor function. At the moment you are wrapping the Promise inside of the setTimeout callback. See [What is the JavaScript version of sleep()?](https://stackoverflow.com/q/951021) — Nick Parsons, Dec 13 '20 at 11:36

eol · Accepted Answer · 2020-12-13T11:52:12.877

3

You need to wrap the setTimeout call in a promise and then resolve the result, so it should look something like this:

const {performance} = require('perf_hooks');

async function executeAndMeasure(fn) {
    const startTime = performance.now();
    const result = await fn();
    const endTime = performance.now();

    const executionTime = endTime - startTime;
    console.log(`Executed in ${executionTime} ms`);

    return result;
}

function someFnThatReturnsAPromise() {
    return new Promise(resolve => {
        setTimeout(() => {
            resolve("Hello World");
        }, 3000);
    })
}

async function someAsyncFunction() {
    return 123;
}

(async () => {
    let result = await executeAndMeasure(someFnThatReturnsAPromise);
    console.log(`result was ${result}`);
    result = await executeAndMeasure(someAsyncFunction);
    console.log(`result was ${result}`);
})();

edited Dec 13 '20 at 11:52

answered Dec 13 '20 at 11:36

eol

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It works! But just one more question: that code actually comes from my unit tests. So to call another `async` function, do I've to wrap it in a promise? – chenny Dec 13 '20 at 11:49
It it's already `async`, no. Defining a method `async` automatically returns the return value in a promise. See my edit. – eol Dec 13 '20 at 11:50
I undestand. Is it easy to enable the `measure` function to call also callbacks with parameters? – chenny Dec 13 '20 at 12:12
Nowadays I'd always try to avoid callbacks as `async/await` allows for much cleaner code. If you really want to do it, you'd have to do the calculation for the `executionTime` in the callback. – eol Dec 13 '20 at 12:17

Node measure execution time - return value from an async passed as parameter to another function

1 Answers1