https://github.com/krzkaczor/babel-plugin-tailcall-optimization

Tail call optimization for JavaScript!
https://github.com/krzkaczor/babel-plugin-tailcall-optimization

babel javascript tail-call-optimization

Last synced: 6 days ago
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Tail call optimization for JavaScript!

• Host: GitHub
• URL: https://github.com/krzkaczor/babel-plugin-tailcall-optimization
• Owner: krzkaczor
• License: mit
• Created: 2016-08-09T23:45:12.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2022-01-09T23:59:33.000Z (almost 3 years ago)
• Last Synced: 2024-10-23T08:27:13.842Z (13 days ago)
• Topics: babel, javascript, tail-call-optimization
• Language: JavaScript
• Size: 76.2 KB
• Stars: 193
• Watchers: 13
• Forks: 9
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# babel-plugin-tailcall-optimization

[![JavaScript Style Guide](https://img.shields.io/badge/code%20style-standard-brightgreen.svg)](http://standardjs.com/)

Tail call optimization for JavaScript!

## Installation

```bash

npm install babel-plugin-tailcall-optimization --save-dev

```

and add to your `.babelrc`:

```js

"plugins": ["tailcall-optimization"]

```

*if you use babel@6 use `babel-plugin-tailcall-optimization@1` package*

## How does it work?

We rewrite functions with tail calls to ones using while loops. Original function with tail call:

```js

function counter (n, acc = 0) {

  if (n === 0) {

    return acc

  } else {

    return counter(n - 1, acc + 1)

  }

}

```

gets rewritten to this:

```js

function counter(n, acc = 0) {

  var _repeat = true;

  var _n, _acc;

  while (_repeat) {

    _repeat = false;

    if (n === 0) {

      return acc;

    } else {

      _n = n - 1

      _acc = acc + 1

      n = _n

      acc = _acc

      _repeat = true;

      continue;

    }

  }

}

```

Plugin does not affect functions without TCOs so it's safe to use.

## Benchmarks

For [Fibonacci Sequence example](https://github.com/krzkaczor/babel-plugin-tailcall-optimization/blob/master/examples/fibonacciSeq.js) benchmark.js results are:

```

Fibonacci Sequence without TCO x 270,170 ops/sec ±1.14% (85 runs sampled)

Fibonacci Sequence with TCO x 1,298,276 ops/sec ±1.24% (83 runs sampled)

```

So function after TCO optimization is almost **5 times faster**.

[Benchmark code](https://github.com/krzkaczor/babel-plugin-tailcall-optimization/blob/master/benchmark/fibonacciSeq.js)

 

## Known issues

 - Currently when plugin detects function creation within tailcalled function it does not optimize it. It's related to difficulties in implementation (function scoping rules). Read more: https://phabricator.babeljs.io/T6869

 - It does not work for mutual recursive functions. I guess it's not super big problem - even JVM does not do this.