Waterfall flow

var input

// Synchronous code
var a_ = a(input)
var b_ = b(a_)
var output = c(b_)

// Synchronous code, short
var output = c(b(a(_)))

// Asynchronous code, callbacks
var status
a(input, function (err, a_) {
  if (err) throw new Error()
  b(a_, function (err, b_) {
    if (err) throw new Error()
    c(b_, function(err, c_) {
      if (err) throw new Error()
      output = c_
    })
  })
})

// Asynchronous code, promises
var output
a(input)
.then(function (a_) {
    return b(a_)
})
.then(function (b_) {
    return c(b_)
})
.then(function (c_) {
  output = c_
})
.catch(function (err) {
  console.error(err)
})

// Asynchronous code, promises, short
a(input).then(b).then(c)
.then(function (c_) {
  output = c_
})
.catch(function (err) {
  console.error(err)
})

// Asynchronous code, generators+co
var a_ = yield a(input)
var b_ = yield b(a_)
var output = yield c(b_)

// Asynchronous code, generators+co, short
var output = yield c(yield b(yield a(input)))