Question

Is there a way to pass information to an async.js parallel call so I don’t have to use global variables?

async.parallel([
  function(callback){
      setTimeout(function(){
          callback(null, 'one');
      }, 200);
  },
    function(callback){
      setTimeout(function(){
          callback(null, 'two');
      }, 100);
  },
],
// optional callback
function(err, results){
  console.log(info)
    // the results array will equal ['one','two'] even though
  // the second function had a shorter timeout.
});

I would like for the final callback to be aware of the value of “info”. Thanks for your help!

Answer 1

To avoid introducing a global variable you could place it within an enclosure:-

(function() {
    var info = "Some info";

    async.parallel([
        function(callback) {
            setTimeout(function() {
                callback(null, "one");
            }, 200);
        }, 
        function(callback) {
            setTimeout(function() {
                callback(null, "two");
            }, 100);
        }
    ], 
    function(error, result) {
        console.log(info);
    });

}) ();

That way the final callback has access to it but it won’t be visible outside of the scope of the anonymous self-executing function that encloses that code.

EDIT To do an enclosure in coffeescript:-

(() ->
  # my code
)()