porter2    

Fast JavaScript implementation of the [porter2] English [stemming] algorithm.

``console
$ npm install porter2
`

[porter2]: https://snowballstem.org/algorithms/english/stemmer.html
[stemming]: https://en.wikipedia.org/wiki/Stemming

Usage

The package is simple: it has no dependencies and exports a single function
named stem.

Import using CommonJS:

`javascript
const { stem } = require('porter2')
`

Or, import using EcmaScript Modules (through interopability with CommonJS):

`javascript
import { stem } from 'porter2'
`

Use the stemmer:

`javascript
const word = stem('animadversion')
console.log(word) //=> animadvers
`

This stemmer expects a lowercase English word.

The code is compatible with ES5. TypeScript type declarations are included.

Benchmarks

On my machine, the 29.4k test suite executes in ~5.25ms (~5.6M/s throughput) in
a hot loop (~31ms for the first run).

Here is a comparison with some other libraries (you probably should take it with
a little grain of salt):

| library | throughput (node) | throughput (bun) |
| ------------------------------------ | ----------------- | ---------------- |
| porter2 1.0.3 | 5621 kops/s | 6780 kops/s |
| [stemr][] 1.0.0 | 840 kops/s | 920 kops/s |
| [wink-porter2-stemmer][] [^1] 2.0.1 | 340 kops/s | 420 kops/s |

[stemr]: https://github.com/localvoid/stemr
[wink-porter2-stemmer]: https://github.com/winkjs/wink-porter2-stemmer

Here are libraries that implement older porter version 1 (note the behavior is
not identical):

| library | throughput (node) | throughput (bun) |
| ------------------------------------ | ----------------- | ---------------- |
| [porter-stemmer-js][] [^2] 1.1.2 | 3280 kops/s | 3373 kops/s |
| [stemmer][] [^3] 2.0.1 | 2100 kops/s | 1549 kops/s |
| [@stdlib/nlp-porter-stemmer][] 0.2.2 | 1712 kops/s | 1604 kops/s |
| [porter-stemmer][] 0.9.1 | 951 kops/s | 1264 kops/s |

[porter-stemmer-js]: https://github.com/evi1Husky/PorterStemmer
[stemmer]: https://github.com/words/stemmer
[@stdlib/nlp-porter-stemmer]: https://github.com/stdlib-js/nlp-porter-stemmer
[porter-stemmer]: https://github.com/jedp/porter-stemmer

The benchmark code is in bench/run.mjs. This is tested with Node.js v22.14.0
and bun v1.2.10 on Zen 3 (4.5 GHz boosted). The library versions are latest as
of 2025-04-29.

[^1]: wink-porter2-stemmer is 99.97% porter2 compliant (fails on '` cases only)

[^2]: That one has similar goals and, surprisingly, was published just 3 days
before this package! (And after the author started working on porter2.js.)

[^3]: ESM only