Promise Loop

Promise Async Looper.js

"use strict";
console.log('============');
 
(function(){
  var i = 0;
  var iLast = window.performance.now();
  //console.profile("Processing pixels");
  function loop(){
      if (i === 300){
        //console.profileEnd();
      return; };
      var waitTime = window.performance.now() - iLast;
      if (waitTime > 1000/30){
          i = 0;
          //console.timeStamp('bad bad jank!!')
          console.error('bad bad jank!!! wait time between frame: ',waitTime);
      }else{
          console.log('no jank detected');
      }
      iLast = window.performance.now();

      i++;
      requestAnimationFrame(loop);


  }
  requestAnimationFrame(loop);
  
}())
 
function fib(n) {
  return n < 2 ? 1 : fib(n - 1) + fib(n - 2);
}
 
//-----------------------
 
function promiseForEach(list, handler, existingChain){
    return list
        .reduce(function (pChain, item, index, array){
           return pChain.then(function (){
                return handler(item, index, array);
            });
        }, existingChain || Promise.resolve() );
}
function promiseForEachCopy(){
    arguments[0] = arguments[0].slice(0);
    return promiseLooper.apply(this,arguments);
}
 
function resolvePromiseList(promiseList, eachThen, existingChain){
    return promiseList.reduce(function(pChain, eachPromise) {
      return pChain.then(function() {
        return eachPromise;
      }).then(eachThen);
    }, existingChain || Promise.resolve())
}
 
 
 
//----------------------
var processData = function (item,index,array){
    console.log('from:',item,'to:', item * 2);
    array[index] = item * 2;
    return array;
};
 
 
var genPromiseToList = function (item,index,array){
    var waitTime = 1000 * (index+1) * Math.random();
    array[index] = new Promise(function(resolve,reject){
        var ans = 'result: '+  fib(30) + '~' + item + '@waited ';
        setTimeout(function(){
            resolve(ans) ;
        //simluate different time resolve;
        }, waitTime);
    });
    console.log('task:',index, 'with wait time: ', waitTime);
    return array;
};
var lastTime = window.performance.now();
var eachThennable = function(data){
    console.log(data, window.performance.now() - lastTime);
    lastTime = window.performance.now();
}; 
 
 
//----------------
var a = [1,2,3,4,5,6,7,8,9,10];
var b = Promise.resolve(a)
//transform data
.then(function(data){
    console.log('level1 transfrom data',data);
    return promiseForEach(data,processData);
})
//start parallel task
.then(function(data){
    console.log('level2 generate parallel task',data);
    return promiseForEach(data,genPromiseToList);
})
//complete parallel task with sequence, progreeisve enhancement
.then(function(promises){
    console.log('level3 resolve parallel task in sequence',promises);
    return resolvePromiseList(promises, eachThennable);
});
 

 
 
console.log('------------');