| 1 | # run-parallel [](https://travis-ci.org/feross/run-parallel) [](https://npmjs.org/package/run-parallel) [](https://www.gittip.com/feross/)
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| 2 |
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| 3 | ### Run an array of functions in parallel
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| 4 |
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| 5 |  [](https://ci.testling.com/feross/run-parallel)
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| 6 |
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| 7 | ### install
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| 8 |
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| 9 | ```
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| 10 | npm install run-parallel
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| 11 | ```
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| 12 |
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| 13 | ### usage
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| 14 |
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| 15 | #### parallel(tasks, [callback])
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| 16 |
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| 17 | Run the `tasks` array of functions in parallel, without waiting until the previous
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| 18 | function has completed. If any of the functions pass an error to its callback, the main
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| 19 | `callback` is immediately called with the value of the error. Once the `tasks` have
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| 20 | completed, the results are passed to the final `callback` as an array.
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| 21 |
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| 22 | ##### arguments
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| 23 |
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| 24 | - `tasks` - An array containing functions to run. Each function is passed a
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| 25 | `callback(err, result)` which it must call on completion with an error `err` (which can
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| 26 | be `null`) and an optional `result` value.
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| 27 | - `callback(err, results)` - An optional callback to run once all the functions have
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| 28 | completed. This function gets a results array containing all the result arguments passed
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| 29 | to the task callbacks.
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| 30 |
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| 31 | ##### example
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| 32 |
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| 33 | ```js
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| 34 | var parallel = require('run-parallel')
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| 35 |
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| 36 | parallel([
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| 37 | function (callback) {
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| 38 | setTimeout(function () {
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| 39 | callback(null, 'one')
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| 40 | }, 200)
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| 41 | },
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| 42 | function (callback) {
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| 43 | setTimeout(function () {
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| 44 | callback(null, 'two')
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| 45 | }, 100)
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| 46 | }
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| 47 | ],
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| 48 | // optional callback
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| 49 | function (err, results) {
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| 50 | // the results array will equal ['one','two'] even though
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| 51 | // the second function had a shorter timeout.
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| 52 | })
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| 53 | ```
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| 54 |
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| 55 | This module is basically equavalent to
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| 56 | [`async.parallel`](https://github.com/caolan/async#paralleltasks-callback), but it's
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| 57 | handy to just have the one function you need instead of the kitchen sink. Modularity!
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| 58 | Especially handy if you're serving to the browser and need to reduce your javascript
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| 59 | bundle size.
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| 60 |
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| 61 | Works great in the browser with [browserify](http://browserify.org/)!
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| 62 |
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| 63 | ## license
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| 64 |
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| 65 | MIT. Copyright (c) [Feross Aboukhadijeh](http://feross.org).
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