Beginner question about async function inside another function

[António Ramos]

What i want is to create a function to read files and return the files to the caller.

This code is not working!

my func in coffeescript 

fs = require('fs')

InitLoadTasks =->

  a=[]

  fs.readdir __dirname+ '/toRun', (err, files) ->

    if (err) 
      console.log(err)
    a=files

initLoadTasks()

reads files from directory

how do i return the a array as a return value to InitLoadTasks?

[Mark Volkmann]

The initLoadTasks function does something asynchronous, so you need to pass it a callback function that will be invoked when it finishes.

If the only thing you want is a list of the files in a given directory, you don't need to write initLoadTasks. You can just call fs.readdir.

However, supposing you want to do something more, here's how you could write it in JavaScript.

var fs = require('fs');

function initLoadTasks(subDir, cb) {

  fs.readDir(__dirname + '/' + subDir, function (err, files) {

    if (err) {

      return cb(err);

    }

    // do extra processing here

    cb(null, files);

  });

}

initLoadTasks('toRun', function (err, files) {

  // do something with files here after checking err

});

 

--
R. Mark Volkmann
Object Computing, Inc.

[Elliot]

If you're only doing it on startup, you could also use the synchronous version of readdir.

On Sep 11, 2012 7:27 AM, "Mark Volkmann" <r.mark....@gmail.com> wrote:

[António Ramos]

got it

 

why is the first parameter of the callback null in

cb(null, files);

?

 

thank you

António

2012/9/11 Elliot <efo...@firetaco.com>

If you're only doing it on startup, you could also use the synchronous version of readdir.

On Sep 11, 2012 7:27 AM, "Mark Volkmann" <r.mark....@gmail.com> wrote:

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[Mark Volkmann]

Convention is for the first argument to callbacks to be an error description. If there was no error, null is passed.

---

R. Mark Volkmann

Object Computing, Inc.