npm install afterInvoke callback after n calls
``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")
})
}
}
`
`js
var after = require("after")
, next = after(3, logItWorks)
next()
next()
next() // it works
function logItWorks() {
console.log("it works!")
}
`
`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)
}
`
npm install after
npm test`
- Raynos
- defunctzombie
[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