function timeout(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

async function a() {
    await timeout(3000);
    console.log('a')
    return 'a'
}

async function b() {
    await timeout(2000);
    console.log('b')
    return 'b'
}

// serie
// async function run() {
//     await a()
//     await b()
// }

// parallel 1
// async function run() {
//     await Promise.all([a(), b()])
// }


// parallel 2
async function run() {
    let fns = [a, b]
    await Promise.all(fns.map(fn => fn())).then(results => console.log('results', results))
}

run()