Mastering JavaScript Promises

Chaining and nesting promises

Remember chaining in promises in Chapter 2, The JavaScript Asynchronous Model, where we learned all the things about chaining and callback hell handling? This is just same for Node.js using Q.

There are two ways you can chain a promise in Node.js using Q: one is you can chain a promise inside a handler and the other is outside of it.

Let's suppose we are doing multiple things at a time, we can set up the promise chain like this:

f1_promise()
    .then(function() { return s1_promise(); })
    .then(function() { return t1_promise();  })
        ...
    .then(function() { return nth_promise();    });

So, we can say that the ANY_promise() function can contain some behavior, and this will return a promise object that leads to eventually return a ...