nodejs

a-way-run-PromiseAll(unknown-length-array).js

const aRequest = new Promise(resolve => {
    setTimeout(() => {
        resolve('3s')
    }, 3000);
});

const bRequest = new Promise(resolve => {
    setTimeout(() => {
        resolve('1s')
    }, 1000);
});

const aHandler = data => {
    console.log('first handler', data)
}

const bHandler = data => {
    console.log('second handler', data)
}

const requests = [aRequest];
const handlers = [aHandler];

const needBRequest = Math.random() > 0.5;

if (needBRequest) {
    requests.push(bRequest);
    handlers.push(bHandler);
}

Promise.all(requests).then(responses => {
    while (responses.length) {
        handlers.shift()(responses.shift())
    }
});

If you cannot ensure length of your requests array, you can handle responses like this way cause a handler handles a request and Promise.all() resolve result in order.