146 lines
3.5 KiB
Markdown
Executable file
146 lines
3.5 KiB
Markdown
Executable file
# reusify
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[![npm version][npm-badge]][npm-url]
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[![Build Status][travis-badge]][travis-url]
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[![Coverage Status][coveralls-badge]][coveralls-url]
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Reuse your objects and functions for maximum speed. This technique will
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make any function run ~10% faster. You call your functions a
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lot, and it adds up quickly in hot code paths.
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```
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$ node benchmarks/createNoCodeFunction.js
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Total time 53133
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Total iterations 100000000
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Iteration/s 1882069.5236482036
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$ node benchmarks/reuseNoCodeFunction.js
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Total time 50617
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Total iterations 100000000
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Iteration/s 1975620.838848608
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```
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The above benchmark uses fibonacci to simulate a real high-cpu load.
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The actual numbers might differ for your use case, but the difference
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should not.
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The benchmark was taken using Node v6.10.0.
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This library was extracted from
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[fastparallel](http://npm.im/fastparallel).
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## Example
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```js
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var reusify = require('reusify')
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var fib = require('reusify/benchmarks/fib')
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var instance = reusify(MyObject)
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// get an object from the cache,
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// or creates a new one when cache is empty
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var obj = instance.get()
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// set the state
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obj.num = 100
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obj.func()
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// reset the state.
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// if the state contains any external object
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// do not use delete operator (it is slow)
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// prefer set them to null
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obj.num = 0
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// store an object in the cache
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instance.release(obj)
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function MyObject () {
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// you need to define this property
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// so V8 can compile MyObject into an
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// hidden class
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this.next = null
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this.num = 0
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var that = this
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// this function is never reallocated,
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// so it can be optimized by V8
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this.func = function () {
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if (null) {
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// do nothing
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} else {
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// calculates fibonacci
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fib(that.num)
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}
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}
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}
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```
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The above example was intended for synchronous code, let's see async:
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```js
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var reusify = require('reusify')
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var instance = reusify(MyObject)
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for (var i = 0; i < 100; i++) {
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getData(i, console.log)
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}
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function getData (value, cb) {
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var obj = instance.get()
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obj.value = value
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obj.cb = cb
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obj.run()
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}
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function MyObject () {
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this.next = null
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this.value = null
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var that = this
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this.run = function () {
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asyncOperation(that.value, that.handle)
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}
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this.handle = function (err, result) {
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that.cb(err, result)
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that.value = null
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that.cb = null
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instance.release(that)
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}
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}
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```
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Also note how in the above examples, the code, that consumes an istance of `MyObject`,
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reset the state to initial condition, just before storing it in the cache.
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That's needed so that every subsequent request for an instance from the cache,
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could get a clean instance.
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## Why
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It is faster because V8 doesn't have to collect all the functions you
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create. On a short-lived benchmark, it is as fast as creating the
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nested function, but on a longer time frame it creates less
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pressure on the garbage collector.
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## Other examples
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If you want to see some complex example, checkout [middie](https://github.com/fastify/middie) and [steed](https://github.com/mcollina/steed).
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## Acknowledgements
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Thanks to [Trevor Norris](https://github.com/trevnorris) for
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getting me down the rabbit hole of performance, and thanks to [Mathias
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Buss](http://github.com/mafintosh) for suggesting me to share this
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trick.
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## License
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MIT
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[npm-badge]: https://badge.fury.io/js/reusify.svg
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[npm-url]: https://badge.fury.io/js/reusify
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[travis-badge]: https://api.travis-ci.org/mcollina/reusify.svg
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[travis-url]: https://travis-ci.org/mcollina/reusify
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[coveralls-badge]: https://coveralls.io/repos/mcollina/reusify/badge.svg?branch=master&service=github
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[coveralls-url]: https://coveralls.io/github/mcollina/reusify?branch=master
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