Dead-simple Generator implementation preventing callback hell.

a.txt

file:a

b.txt

file:b

index.js

var fs = require('fs');

function run ( fn ) {
  var generator = fn()

  function next( err, data ) {
    var ret = generator.next( data )
    if ( ret.done ) return;

    ret.value( next )
  }
  
  next()
}

run(function *(){
  var a = yield read('a.txt')
  var b = yield read('b.txt')
  console.log( a )
  console.log( b )
})

function read( file ) {
  return function( cb ) {
    fs.readFile( file, 'utf8', cb )
  }
}