Javascript async parallel - How to return the final result/callback?

Question

How to return the final result/callback to the calling function? All examples in the documentation only show console.log() options.

The following code is just for example purposes.

function foo(input) {
    async.parallel([
        function(callback) {
            callback(null, input.one);
        },
        function(callback) {
            callback(null, input.two);
        }
    ],
    function(err, results) {
        // What to do here? all examples include console.log()
        // I want to return the result ([1, 2]) to the calling function!
    });
}

var data = {"one": 1, "two": 2};
var bar = foo(data);

console.log(bar); // Will return [1, 2]

Edit: This question was marked as duplicate. The other post did not explain how this was done to someone with marginal experience with javascript and callbacks.

Add callback to your `foo` function and call it with the result from the final `async` callback. — alexmac, Aug 08 '17 at 16:25
Why are you using `async` if your two functions are not actually asynchronous? — Bergi, Aug 08 '17 at 16:27
@alexmac could you please post the answer? I`m still trying to wrap my head around callbacks :| — Daniel Bjørnådal, Aug 08 '17 at 16:27

score 2 · Answer 1 · answered Aug 08 '17 at 16:26

2

If your function contains async code so it becomes an async function. You need to include a callback :

    function foo(input, cb) {

       async.parallel([
          function(callback) {
              callback(null, input.one);
          },
          function(callback) {
            callback(null, input.two);
          }
      ],
      function(err, results) {
       return cb(results);
      });
   }

And modify your call :

var data = {"one": 1, "two": 2};
foo(data, function(bar){
  console.log(bar);

});

answered Aug 08 '17 at 16:26

Daphoque

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1

Don't ignore the error! Just use `async.parallel([…], cb)` directly. – Bergi Aug 08 '17 at 16:27
1

@DanielBjørnådal `return` statement is not required there. – alexmac Aug 08 '17 at 16:35

Javascript async parallel - How to return the final result/callback?

1 Answers1