README.md
1# After [![Build Status][1]][2]
2
3Invoke callback after n calls
4
5## Status: production ready
6
7## Example
8
9```js
10var after = require("after")
11var db = require("./db") // some db.
12
13var updateUser = function (req, res) {
14 // use after to run two tasks in parallel,
15 // namely get request body and get session
16 // then run updateUser with the results
17 var next = after(2, updateUser)
18 var results = {}
19
20 getJSONBody(req, res, function (err, body) {
21 if (err) return next(err)
22
23 results.body = body
24 next(null, results)
25 })
26
27 getSessionUser(req, res, function (err, user) {
28 if (err) return next(err)
29
30 results.user = user
31 next(null, results)
32 })
33
34 // now do the thing!
35 function updateUser(err, result) {
36 if (err) {
37 res.statusCode = 500
38 return res.end("Unexpected Error")
39 }
40
41 if (!result.user || result.user.role !== "admin") {
42 res.statusCode = 403
43 return res.end("Permission Denied")
44 }
45
46 db.put("users:" + req.params.userId, result.body, function (err) {
47 if (err) {
48 res.statusCode = 500
49 return res.end("Unexpected Error")
50 }
51
52 res.statusCode = 200
53 res.end("Ok")
54 })
55 }
56}
57```
58
59## Naive Example
60
61```js
62var after = require("after")
63 , next = after(3, logItWorks)
64
65next()
66next()
67next() // it works
68
69function logItWorks() {
70 console.log("it works!")
71}
72```
73
74## Example with error handling
75
76```js
77var after = require("after")
78 , next = after(3, logError)
79
80next()
81next(new Error("oops")) // logs oops
82next() // does nothing
83
84// This callback is only called once.
85// If there is an error the callback gets called immediately
86// this avoids the situation where errors get lost.
87function logError(err) {
88 console.log(err)
89}
90```
91
92## Installation
93
94`npm install after`
95
96## Tests
97
98`npm test`
99
100## Contributors
101
102 - Raynos
103 - defunctzombie
104
105## MIT Licenced
106
107 [1]: https://secure.travis-ci.org/Raynos/after.png
108 [2]: http://travis-ci.org/Raynos/after
109 [3]: http://raynos.org/blog/2/Flow-control-in-node.js
110 [4]: http://stackoverflow.com/questions/6852059/determining-the-end-of-asynchronous-operations-javascript/6852307#6852307
111 [5]: http://stackoverflow.com/questions/6869872/in-javascript-what-are-best-practices-for-executing-multiple-asynchronous-functi/6870031#6870031
112 [6]: http://stackoverflow.com/questions/6864397/javascript-performance-long-running-tasks/6889419#6889419
113 [7]: http://stackoverflow.com/questions/6597493/synchronous-database-queries-with-node-js/6620091#6620091
114 [8]: http://github.com/Raynos/iterators
115 [9]: http://github.com/Raynos/composite
116
