01-callbacks.js

function getAnAnswerMaybeSomeDay(url,cb){
  var willWork = Math.random() > .1
  var waitFor = Math.random() * 500
  setTimeout(function(){
    if(willWork){
      cb(null,"réponse")
    }else{
      cb(new Error("pas de reponse"))
    }
  },waitFor)
}

function doSomethingWithData(data,cb){
  var willWork = Math.random() > .1
  var waitFor = Math.random() * 500
  setTimeout(function(){
    if(willWork){
      cb(null,data+" > traitement 1")
    }else{
      cb(new Error('erreur durant traitement 1'))
    }
  },waitFor)
}

function doSomethingElseWithData(data){
  return data+" > traitement 2"
}

function giveMeAnAnswer(cb){
  getAnAnswerMaybeSomeDay('www.facebook.com',function(err,res){
    if(err){return cb(err);}
    doSomethingWithData(res,function(err,processed){
        if(err){return cb(err);}
        try{
          var processedMore = doSomethingElseWithData(processed)
          cb(null,processedMore)
        }catch(e){
            return cb(e)
        }
    })
  })
}

giveMeAnAnswer(function(err,final){
  if(err){
    console.error(err.message)
  }else{
    console.log(final)
  }
})

02-promises.js

function getAnAnswerMaybeSomeDay(url){
  return new Promise(function(resolve,reject){
    var willWork = Math.random() > .1
    var waitFor = Math.random() * 500
    setTimeout(function(){
      if(willWork){
        resolve("réponse")
      }else{
        reject(new Error("pas de reponse"))
      }
    },waitFor)
  })
}

function doSomethingWithData(data){
  return new Promise(function(resolve,reject){
    var willWork = Math.random() > .1
    var waitFor = Math.random() * 500
    setTimeout(function(){
      if(willWork){
        resolve(data+" > traitement 1")
      }else{
        reject(new Error('erreur durant traitement 1'))
      }
    },waitFor)
  })
}

function doSomethingElseWithData(data){
  return data+" > traitement 2"
}

function giveMeAnAnswer(){
  return getAnAnswerMaybeSomeDay('www.facebook.com')
    .then(doSomethingWithData)
    .then(doSomethingElseWithData)
    .catch(function(err){throw err;})
}

giveMeAnAnswer()
  .then(function(answer){
    console.log(answer)
  })
  .catch(function(err){
    console.error(err.message)
  })