How To Use Jquery Deferred (when/then, Etc.) To Fix Asynchroneous Pyramid Of Doom Issue

I've been puzzling for quite a while trying to wrap my head around JavaScript promises. I want to fix some issues with asynchroneous calls in my code, to de-spagethise it. But I'd

Solution 1:

But I can't get it to work

Some points:

• don't use an array of deferreds, even less a global one! Break it into single steps, and use a single promise for each step.
• use the counter value to resolve the promise. A promise should always represent an (async) result.
• don't use $.when unless you need to wait for multiple promises
• then does take a callback function. You must not call takeStep(), but pass it.

You also might want to have a look at this answer for rules-of-thumb to get familiar with promises.

// the most generic function that only waits and returns a promisefunctionwait(t, v) {
    var d = new $.Deferred();
    setTimeout(function() {
        d.resolve(v);
    }, t);
    return d.promise();
}

// logs the value and returns the next numberfunctionmarkStep(nr) {
    log('step ' + cntr + ': ' + getCurrentTime() );
    return nr+1;
}
// waits before logging and returns a promise for the next numberfunctiontakeStep(nr) {
    returnwait(stepTime, nr).then(markStep);
}

takeStep(0)
.then(takeStep)
.then(takeStep)
.then(takeStep)
.then(takeStep)
.done(function(nr) {
    log('done (' + getCurrentTime() + ')');
});