I think Promise pattern is evolution. but not ready.

Promise/My (I think)

Current promise pattern in action.

Promise/A or A+ Standard

var promise = new Promise(function(resolve, reject){
  var i = 0;
  setInterval(function(){
    resolve(++i); // when fired, this promise will flag with DONE.
  });
});
promise.then(function(i){
  console.log(i);
}).then(function(i){
  console.log(i);
});

Console output as,

1

1

Yes, when call resolve function, that promise will think "My promise has done!".

then, setInterval is still calling with increase variable i but never bring to then argument.

well. that's right. true. true.

but, I want to more transfer infomation to promise object. what should I do?

Future promise pattern more can do anything I think.

Plan A : one more promise arguments, one more case callback.

same as current promise pattern, just add one more optional arguments named as progress

and when calling then, define one more function arguments for handling progress.

var promise = new Promise(function(resolve, reject, progress){
  var i = 0;
  setInterval(function(){
    if(i<100){
      progress(++i);
    }else{
      resolve(i);
    }
  },1000);
});
promise.then(function(val){
  console.log("It's done!" + val + "%");
}, function(err){
  console.error("Oh, NO!" + err);
}, function(val){
  console.log("loading..." + val + "%");
});

This example is increase interger variable i at every seconds, and transfer to progress.

and run simple progress handler in 3rd argument of then function.

when i incresed 100, call resolve with increased value, and... well.. same as current promise pattern.

that's all.

• GOOD :
• compatibility with current promise pattern.
• BAD :
• looks more dirty in then method.

I'll think more ways.