async.js

var foo

async.waterfall([
  function(cb) {
    getThingFromDB("foo", cb)
  }, function(_foo, cb) {
    foo = _foo
    getOtherThingFromDB(foo, "bar", cb)
  }, function(bar, cb) {
    qux(foo, bar)
  }
])

promises.js

var foo = getThingFromDB("foo")

var bar = foo.then(function(foo) {
  return getOtherThingFromDB(foo, "bar")
})

promise.all([foo, bar]).then(function(foo, bar) {
  qux(foo, bar)
})

sync.js

var foo = getThingFromDB("foo"),
    bar = getOtherThingFromDB(foo, "bar")

qux(foo, bar)

minor update for promises.js

var foo = getThingFromDB("foo")

var bar = foo.then(function(foo) {
  return getOtherThingFromDB(foo, "bar")
})

promise.all([foo, bar]).then(quux)