Promise.map not returning right order

Question

using bluebird how can i do the following work.

 groupCast = [Promise.resolve("name1"), Promise.resolve("name2"),Promise.resolve("name3")]

    Promise.map( groupCast , function (group){
        Promise.resolve($http.get("/getdata" , params:{group:group}))
               .then(function(response){ console.log(group," done")return response}))
        return response

        })
              .then(function(resp){console.log(resp)})

if the response for each group for the http call was "one" , "two" , "three" We would then expect to have:

"name1 done";
"name2 done";
"name3 done";
[ "one" , "two" ,"three" ]

However i get

 [ "one" , "two" ,"three" ]
    "name1 done";
    "name2 done";
    "name3 done";

How could I fix it. i cannot use async and wait because its not supported by IE.

Answer 1

First off, your code formatting makes it a bit hard to see what's going on. Let me clean it up a bit and add some comments so you can see what's happening.

Promise.map(groupCast, function(group) {
  //the following kicks off a new promise, which is not chained to the current one
  Promise.resolve($http.get("/getdata", { params: { group: group } })).then(
    function(response) {
      console.log(group, " done");
      //you're returning response below, but it's not going anywhere!
      return response;
    }
  );
  //The current promise resolves right away, not waiting for the $http call.
  //Also, you're returning an undefined value here.
  return response;
}).then(function(resp) {
  //the prior promise resolves with undefined.
  console.log(resp);
});

Now let's fix it so the promises chain properly.

Promise.map(groupCast, function(group) {
  // $http.get returns a promise already. No need to wrap it in one.
  // Also, let's go ahead and return the chained promise so the `map` function can wait for it.
  return $http.get("/getdata", { params: { group: group } })
    .then(function(response) {
        console.log(group, " done");
        return response;
      });
}).then(function(resp) {
  //the prior promise should now resolve as expected.
  console.log(resp);
});