Example use of ES6 generator with 'co' and 'thunkify' modules to read four files in series.

co-generator-ex0.js

#!/usr/bin/env node --harmony-generators
var fs = require('fs')
  , thunkify = require('thunkify')
  , co = require('co')
  , readFile = thunkify(fs.readFile)
  , fns = ["file0.txt", "file1.txt"
          , "file2.txt", "file3.txt"]

co(function*(){
  var contents = '', i
  for (i=0; i<fns.length; i+=1) {
    contents += yield readFile(fns[i])
  }
  console.log(contents)
})()