porter2
Version:
Fastest JavaScript implementation of the porter2 stemmer
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# porter2 [](https://www.npmjs.com/package/porter2) [](https://github.com/eilvelia/porter2.js/actions/workflows/ci.yml)
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