SOURCE

const awaitWrap = (promise) => {
    return promise
        .then(data => [null, data])
        .catch(err => [err, null]);
}

const fn1 = () => {
    return new Promise((resolve) => {
        setTimeout(() => {
            console.log('fn1')
            resolve("fn1 √")
        }, 2000)
    })
}

const fn2 = () => {
    return new Promise((resolve) => {
        setTimeout(() => {
            console.log('fn2')
            resolve("fn2 √")
        }, 2000)
    })
}

const fn3 = () => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('fn3')
            reject("fn3 ×")
        }, 2000)
    })
}

async function fna() {
    let a = await fn1();
    let b = await fn2();
    console.log(a + b);
}

async function fnb() {
    let a1 = fn1();
    let b1 = fn2();
    let a = await a1;
    let b = await b1;
    console.log(a + b);
}

async function fnc() {
    let [err, data] = await awaitWrap(fn3());
    if (err)
        //do something
    console.log('err', err);
    console.log('data', data);
}

// fna();
// fnb();
fnc();

// function awaitWrap<T, U = any>(promise: Promise<T>): Promise<[U | null, T | null]> {
//     return promise
//         .then<[null, T]>((data: T) => [null, data])
//         .catch<[U, null]>(err => [err, null])
// }