HORIZON PROJECT

# After [![Build Status][1]][2]

Invoke callback after n calls

## Status: production ready

## Example

```js

var after = require("after")

var db = require("./db") // some db.

var updateUser = function (req, res) {

  // use after to run two tasks in parallel,

  // namely get request body and get session

  // then run updateUser with the results

  var next = after(2, updateUser)

  var results = {}

  getJSONBody(req, res, function (err, body) {

    if (err) return next(err)

    results.body = body

    next(null, results)

  })

  getSessionUser(req, res, function (err, user) {

    if (err) return next(err)

    results.user = user

    next(null, results)

  })

  // now do the thing!

  function updateUser(err, result) {

    if (err) {

      res.statusCode = 500

      return res.end("Unexpected Error")

    }

    if (!result.user || result.user.role !== "admin") {

      res.statusCode = 403

      return res.end("Permission Denied")

    }

    db.put("users:" + req.params.userId, result.body, function (err) {

      if (err) {

        res.statusCode = 500

        return res.end("Unexpected Error")

      }

      res.statusCode = 200

      res.end("Ok")  

    })   

  }

}

```

## Naive Example

```js

var after = require("after")

    , next = after(3, logItWorks)

next()

next()

next() // it works

function logItWorks() {

    console.log("it works!")

}

```

## Example with error handling

```js

var after = require("after")

    , next = after(3, logError)

next()

next(new Error("oops")) // logs oops

next() // does nothing

// This callback is only called once.

// If there is an error the callback gets called immediately

// this avoids the situation where errors get lost.

function logError(err) {

    console.log(err)

}

```

## Installation

`npm install after`

## Tests

`npm test`

## Contributors

 - Raynos

 - defunctzombie

## MIT Licenced

  [1]: https://secure.travis-ci.org/Raynos/after.png

  [2]: http://travis-ci.org/Raynos/after

  [3]: http://raynos.org/blog/2/Flow-control-in-node.js

  [4]: http://stackoverflow.com/questions/6852059/determining-the-end-of-asynchronous-operations-javascript/6852307#6852307

  [5]: http://stackoverflow.com/questions/6869872/in-javascript-what-are-best-practices-for-executing-multiple-asynchronous-functi/6870031#6870031

  [6]: http://stackoverflow.com/questions/6864397/javascript-performance-long-running-tasks/6889419#6889419

  [7]: http://stackoverflow.com/questions/6597493/synchronous-database-queries-with-node-js/6620091#6620091

  [8]: http://github.com/Raynos/iterators

  [9]: http://github.com/Raynos/composite