micahstubbs / fast-memoize.js

:rabbit2: Fastest possible memoization library

fast-memoize.js

 

In computing, memoization is an optimization technique used primarily to speed up computer programs by storing the results of expensive function calls and returning the cached result when the same inputs occur again. — Wikipedia

This library is an attempt to make the fastest possible memoization library in JavaScript that supports N arguments.

Installation

To use the library, install it through npm

npm install fast-memoize --save

To port it to Browser or any other (non CJS) environment, use your favorite CJS bundler. No favorite yet? Try: Browserify, Webmake or Webpack

Usage

const memoize = require('fast-memoize')

const fn = function (one, two, three) { /* ... */ }

const memoized = memoize(fn)

memoized('foo', 3, 'bar')
memoized('foo', 3, 'bar') // Cache hit

Custom cache

The fastest cache is used for the running environment, but it is possible to pass a custom cache to be used.

const memoized = memoize(fn, {
  cache: {
    create() {
      var store = {};
      return {
        has(key) { return (key in store); },
        get(key) { return store[key]; },
        set(key, value) { store[key] = value; }
      };
    }
  }
})

The custom cache should be an object containing a create method that returns an object implementing the following methods:

• get
• set
• has

Custom serializer

To use a custom serializer:

const memoized = memoize(fn, {
  serializer: customSerializer
})

The serializer is a function that receives one argument and outputs a string that represents it. It has to be a deterministic algorithm meaning that, given one input, it always returns the same output.

Benchmark

For an in depth explanation on how this library was created, go read this post on RisingStack.

Below you can see a performance benchmark between some of the most popular libraries for memoization.

To run the benchmark, clone the repo, install the dependencies and run npm run benchmark.

git clone [email protected]:caiogondim/fast-memoize.git
cd fast-memoize
npm install
npm run benchmark

Against another git hash

To benchmark the current code against a git hash, branch, ...

npm run benchmark:compare 53fa9a62214e816cf8b5b4fa291c38f1d63677b9

Gotchas

Spread arguments

We check for function.length to get upfront the expected number of arguments in order to use the fastest strategy. But with spread arguments we don't receive the right number.

function multiply (multiplier, ...theArgs) {
  return theArgs.map(function (element) {
    return multiplier * element
  })
}
multiply.length // => 1

So if you use spread arguments, explicitly set the strategy to variadic.

const memoizedMultiply = memoize(multiply, {
  strategy: memoize.strategies.variadic
})

Credits

• Icon by Mary Rankin from the Noun Project
• Bullet train ZSH theme

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