porter2  

Fast JavaScript implementation of the porter2 English stemming algorithm.

$ npm install porter2

Usage

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

Import using CommonJS:

const { stem } = require('porter2')

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

import { stem } from 'porter2'

Use the stemmer:

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

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

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.

Footnotes

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 ↩