How to handle asynchronous operations in StateMachine?

Im am not completely sure, but there seems to be a simple solution with the already existing Espruino StateMachine module:

Why no do the actual asynchronous work in the "enter" function of each state, and then trigger a state transition in the last "then" block of the chained Promises as follows:

function enterOne() {
    console.log("Enter One...");

    new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve('good');
        }, 5000);
    })
    .then((result) => {
        sm.signal(result);
    })
    .catch(() => {
        sm.signal('bad');
    });
};

In the "signal" function of the respective state there could be code that decides - based on the parameter on the "signal" call (here: 'good' or 'bad') - to which new state to transition:

function signalOne(result, e) { 

    console.log("signal one with parameters", result, e);
    if ('good' === result) {
        return {state:'Two', wait:(e)?e:0};
    } else if ('bad' === result) {
        return {state:'Error', wait:(e)?e:0};
    }
};

I think this will fit my needs.