Angularjs Chain Promises Sequentially Within For Loop

How do i chain promises sequentially within for loop, i have seen lot of examples on google to do this but i couldn't implement for my case: i have gone through this link for seque

Solution 1:

Here's what I came up with. You'll need to reduce the array into a single promise.

var results = [...];
var sequentialPromise = results.reduce(function(a, b) {
  return a.then(function(){
   return doSomething(b);
  });
}, $q.resolve());

sequentialPromise.then(function(){...});

Solution 2:

So here is an example on how you would do the sequential promises with Q, also some improvements on how to do your promises so you can properly catch errors thrown at any point in your promise chain. You must always make sure to return a promise on any method that uses them. Also avoid pyramid code by not nesting the .then to make your code cleaner:

ServiceA.login()
    .then(function(response){
        // you must always return your promisereturn ServiceA.sync()

    })
    // don't nest the .then make them flat like this
    .then(function(response){

    })
    .catch(function(){
        // if you made sure to always return your promises this catch will catch any errors throws in your promise chain including errors thrown by doSomething()
    });

functionsync(){
    // you must always return your promisereturn ServiceB.complete()
        .then(function(){

            var result = $q.when();
            angular.forEach(response, function (value) {
                result = result.then(doSomething(value));
            });
            return result;
        })
        .then(function(){
            // the array of promises has run sequentially and is completed
        });

}