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.

[^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