Passing parameters to forEach Iterator in nodejs async

Question

Passing parameters to forEach Iterator in nodejs async

I'm trying to pass parameters to the iterator function that the async node module requires.

async.forEach dbReply, mediaHandler(entry, event.folder, callback), (error) ->
   console.log error 

mediaHandler = (entry, folder, callback) ->
   console.log arguments

I constantly get ReferenceError: entry is not defined

Any clue on how can I pass the event.folder parameter to the function?

javascript
node.js
coffeescript
async.js

Answer 1

Sounds like you want your mediaHandler function to return an iterator function:

mediaHandler = (folder, callback) ->
    (entry) ->
        # Do things with folder, callback, and entry.
        # folder and callback are available through the closure,
        # entry is supplied by forEach.

and then:

async.forEach dbReply, mediaHandler(event.folder, callback), (error) -> ...

Your entry argument is supplied by forEach when it calls the iterator but the other two arguments are (presumably) available when you're calling async.forEach so you're trying to curry a three argument mediaHandler to get a one argument function that forEach can deal with; there are other ways to do that in (Coffee|Java)Script but doing it by hand with a closure is probably the simplest.