Adding Error Management to our own Async-Await

Add error management to the home-made Async-Await implementation you did in the previous lab so that a program like this:

import { awaitFor, waiter } from './async-await.mjs';

function doTask1(arg) {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(arg), 100)
    })
}

function doTask2(arg) {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(arg + 2), 100)
    })
}

function doTask3(arg) {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(arg + 3), 100)
    })
}

function doTaskErr(arg) {
    return new Promise((resolve, reject) => {
        setTimeout(() => reject("Ay!!!!!!!!", 100))
    })
}

function* init(arg) {

    const res1 = yield doTask1(arg);
    console.log(res1);

    const res2 = yield doTask2(res1);
    console.log(res2);

    const res3 = yield doTask3(res2);
    console.log(res3);

    return res3;
}

function* fails(arg) {
    try {
        console.log("Error handling example");

        const res1 = awaitFor(yield doTask1(arg));
        console.log(res1);

        const res2 = awaitFor(yield doTaskErr(res1));
        console.log(res2);

        const res3 = awaitFor(yield doTask3(res2));
        console.log(res3);

        return res3;
    } catch (err) {
        console.log(`Inside "fails" catch: ${err}`);
    }
}

function* main() {
    try {
        const res = awaitFor(yield waiter(init, 3)());
        console.log(`res=${res}`);
        awaitFor(yield waiter(fails, 3)());
        console.log(`Executed since the error was catched`);
    } catch (err) {
        console.log(`Inside "main" catch: ${err}`);
    }
}

waiter(main)();

should produce an output like this:

➜  async-await-equal-generators-plus-promises git:(trycatch) node solution.mjs
3
5
8
res=8
Error handling example
3
Inside "fails" catch: Ay!!!!!!!!
Executed since the error was catched

Delivery

Use the repository created for the previous lab. Create a branch called trycatch and develop your solution to this lab in it.

See

• Async-Await ≈ Generators + Promises (opens new window) at https://hackernoon.com/ (opens new window) Cha on July 26th 2017
• Repo ULL-MII-SYTWS-2021/async-await-equal-generators-plus-promises (opens new window) (private)
• Optional chaining (?.)