Pyramid of doom is a classic scenario where we have tons of nesting or branching. This makes the code overly complex and the unit testing a very complex job:

promise1()
    .then((resp) => {
        promise2(resp)
            .then((resp2) => {
                promise3(resp2)
                    .then((resp3) => {
                        if(resp3.something) {
                            // do something
                        } else {
                            // do something else
                        }
                    });
            });
    });

Instead, do the following:

promise1()
    .then((resp) => {
        return promise2(resp);
    })
   .then((resp2) => {
        return promise3(resp2);
    })                
    .then((resp3) => {
        if(resp3.something) {
            // do something
        } else {
            // do something else
        }
    })