Promise Based processing with Array. sequentialProcess and parallelProcess

jsbin.yecewaj.js

//Author - Narendra Sisodiya - http://narendrasisodiya.com

//WHeN to use ? when async result from One Element is needed in another.

var sequentialProcess = function(arr, callback){
  var pp = Promise.resolve();
  arr.forEach(function(v, i, A){
   pp = pp.then(function(){
     return callback(v, i, A);
   });
  });
  return pp;
}

//WHeN to use ? when async result from One Element is NOT needed in another.
var parallelProcess = function(arr, callback){
  var pArray = [];
  arr.forEach(function(v, i, A){
    pArray.push(callback(v, i, A));
  });
  return Promise.all(pArray);
}

var arr = ["A", "B", "C", "D", "E"];

sequentialProcess(arr, function(val){
  console.log("Processing... " + val + " Started")
  return new Promise(function(resolve){
    window.setTimeout(function(){
      console.log("Processing " + val + " Done");
      resolve();
    }, Math.random()*2000+1000)
  });
}).then(function(){
  console.log("ALL Done");
});

/*
sequentialProcess Will Result in following.

"Processing... A Started"
"Processing A Done"
"Processing... B Started"
"Processing B Done"
"Processing... C Started"
"Processing C Done"
"Processing... D Started"
"Processing D Done"
"Processing... E Started"
"Processing E Done"
"ALL Done"
*/


/*
parallelProcess Will Result in following.
"Processing... A Started"
"Processing... B Started"
"Processing... C Started"
"Processing... D Started"
"Processing... E Started"
"Processing C Done"
"Processing A Done"
"Processing B Done"
"Processing E Done"
"Processing D Done"
"ALL Done"
*/