Promises not working as expected with async.each - node.js

Question

I'm somehow not able to find the solution. Here is what I'm doing:
async.each(bottles, function(bottle) {
// set substance quantity to 0
updateQuantity(bottle[constant.SUBSTANCE_ID], 0)
.then(function() {
bottle[constant.EXPIRY] = expiry;
bottle[constant.IS_AVAILABLE] = true;
updateRecord(bottle)
.then(function() {
console.log('Updated');
},
function() {});
}, function() {});
}, function() {
console.log('Finished');
});
console.log('Done');
The method updateQuantity and updateRecord returns promises and are using Knex update in the background which also returns a promise.
I want the output of the above code to be:
Updated
Updated
Finished
Done
But the output I'm getting is:
Done
Updated
Updated
So, the callback of async.each is not working and the code is not waiting for async.each to finish.

Answer 1

You have to call the passed in callback from the async.each operation. As it is, async doesnt know when your callback resolves.
Also, DONE should always be the first text you see as async.each doesn't block. When you start running running the script, async.each will be registered, but because your code is asynchronous it will reach the console.log('Done') before the updateRecord and updateQuantities complete
async.each(bottles, function(bottle, callback) {
updateQuantity(bottle[constant.SUBSTANCE_ID], 0)
.then(function() {
...
updateRecord(bottle)
.then(function() {
console.log('Updated');
callback();
},
function() {});
}, function() {});
}, function() {
console.log('Finished');
});
console.log('Done');

Answer 2

Don't use async.js at all with promises, they are capable of what you need with their builtin methods and you don't need to fall back to callbacks.
bottles.reduce(function(prev, bottle) {
return prev.then(function() {
// set substance quantity to 0
return updateQuantity(bottle[constant.SUBSTANCE_ID], 0)
}).then(function() {
bottle[constant.EXPIRY] = expiry;
bottle[constant.IS_AVAILABLE] = true;
return updateRecord(bottle);
}).then(function() {
console.log('Updated');
});
}, Promise.resolve()).then(function() {
console.log('Finished successfully');
}, function(err) {
console.error(err)
}).then(function() {
console.log('Done'); // notice you must put this in the callback
});
console.log('Started');