README.md

Exercise 02 - Async Google Ping Tester

This exercise tests basic knowledge about Promises, async, and await. We build a simple function that pings a given URL and returns the response time. If the URL does not reply within a given timeout, the function rejects with a TimeoutError.

Tasks

• implement the function throwAfter(ms) that rejects after the given amount of milliseconds. The thrown error should be an instance of TimeoutError. Keep in mind that this async function never returns a value. What is the correct return type here?
• implement the function withTimeout(promise, timeout) that wraps the given promise to reject after the given timeout or return the value of the promise whichever comes faster.
• Bonus Task: modify the pingUrl(url) function to also return the duration of the request.

Hints

Delay a method call with setTimeout():

setTimeout(() => console.log("Hello"), 1000);

Static Promise methods:

Promise.resolve(1234); // resolves with 1234
Promise.reject(new Error("error")); // rejects with an error
Promise.all([promise1, promise2]); // resolves once all promises resolve, rejects if one rejects
Promise.race([promise1, promise2]); // resolves once the first promise resolves, rejects if the first rejects

Object unwrapping:

// with objects
const object = {a: 1, b: "two :)", c: () => 3};
console.log(object.a); // 1
const {a, b, c} = object;
console.log(a); // 1

// with arrays
const array = [1, 2, 3];
const [first, second, third] = array;
console.log(first); // 1

Measuring time:

const now = Date.now();
await someAsyncMethod();
const duration = Date.now() - now; // in ms