Asynchronous function inside async.each is not getting fired

Question

Can anyone explain the order in which below console logs are getting printed? I am using async version 1.4.23 .
response contains two items.
output: label 1
label 2
label 2
label 4
label 3
label 3

async.parallel([
  function(callback){
    detailsData.list({}, function(err, response) {
      if (!err) {
        console.log("label 1");
        async.each(response, function(item, cb) {
          console.log("label 2");
          itemList.getData(item, function(err, response) {
            console.log("label 3");
            }
            cb(err);
          });
        });
      }
      callback(err);
    });  
  },
  function (callback) {
    somefunction();
  }], function (err) {
    console.log("label 4");
  }  

Why is label 3 not printed before label 4?

Answer 1

You will have to pass the callback that you get from async.parallel to async.each instead of invoking it immediately, otherwise the parallel execution won't wait for the each.

async.parallel([
  function(callback){
    detailsData.list({}, function(err, response) {
      if (err) return callback(err); // <- still call it when you're not going for the each
      console.log("label 1");
      async.each(response, function(item, cb) {
        console.log("label 2");
        itemList.getData(item, function(err, response) {
          console.log("label 3");
          cb(err, response);
        });
      }, callback);
//       ^^^^^^^^
    });
  },
  function(callback) {
    somefunction();
    callback();
  }
], function(err) {
  console.log("label 4");
});