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