root / HServer / 00.Server / 00.Program / node_modules / after / README.md
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| 1 | 39 | HKM | # After [![Build Status][1]][2] |
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| 2 | |||
| 3 | Invoke callback after n calls |
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| 4 | |||
| 5 | ## Status: production ready |
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| 6 | |||
| 7 | ## Example |
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| 8 | |||
| 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 | |||
| 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 | |||
| 20 | getJSONBody(req, res, function (err, body) {
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| 21 | if (err) return next(err) |
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| 22 | |||
| 23 | results.body = body |
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| 24 | next(null, results) |
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| 25 | }) |
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| 26 | |||
| 27 | getSessionUser(req, res, function (err, user) {
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| 28 | if (err) return next(err) |
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| 29 | |||
| 30 | results.user = user |
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| 31 | next(null, results) |
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| 32 | }) |
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| 33 | |||
| 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 | |||
| 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 | |||
| 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 | |||
| 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 | |||
| 59 | ## Naive Example |
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| 60 | |||
| 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 | |||
| 65 | next() |
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| 66 | next() |
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| 67 | next() // it works |
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| 68 | |||
| 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 | |||
| 74 | ## Example with error handling |
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| 75 | |||
| 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 | |||
| 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 | |||
| 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 | |||
| 92 | ## Installation |
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| 93 | |||
| 94 | `npm install after` |
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| 95 | |||
| 96 | ## Tests |
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| 97 | |||
| 98 | `npm test` |
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| 99 | |||
| 100 | ## Contributors |
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| 101 | |||
| 102 | - Raynos |
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| 103 | - defunctzombie |
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| 104 | |||
| 105 | ## MIT Licenced |
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| 106 | |||
| 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 |