foobar.js

// nested
db.call(query, function (err, value) {
  // do stuff here
  nestedFn('foo', function (err, something) {
    // do more stuff here
  })
})

// below
db.call(query, gotValue)

function gotValue(err, value) {
  // do stuff here
  nestedFn('foo', gotSomething)
}

function gotSomething(err, something) {
  // do more stuff here
}