fast-topics

fast-topics

Unsupervised topic extraction from text using Latent Dirichlet Allocation.

Written in Go, using nlp library. Compiled to WebAssembly for use in browsers. Zero JavaScript dependencies.

Bindings written in TypeScript and compiled to JavaScript.

Demo

To see a demo of the algorithm, run npm run demo and go to localhost:8080.

Basic usage

import {getTopics, initialiseWasm} from 'fast-topics'

await initialiseWasm()

const documents = ['quick brown fox', 'cow jumped over moon', 'the crafty fox', 'moon of cheese']
const {docs, topics} = getTopics(documents)
for (const [idx, doc] of Object.entries(docs))
    console.log('Doc', documents[idx], 'Topic', doc[0].topic)
for (const [idx, topic] of Object.entries(topics))
    console.log('Topic', idx, 'words', topic[0].word, topic[1].word, topic[2].word)

See below for how to use with frameworks such as Vite.

Source code

Go code is contained in go directory. The logic is in its own file, and the main.go file just manages the JavaScript bindings and exports.

TypeScript and JavaScript bindings source code is in js.

The compiled outputs are in dist when built with npm run build.

Outputs can be built seperately with these scripts:

npm run build:ts # for typescript only
npm run build:go # for go only

Building WASM from source requires a Go compiler to be installed.

Usage in browsers with frameworks

The WebAssembly module needs to be initialised before the function can be called. The initialisation function is await initialiseWasm(). There are two built in initialisation methods: initWithFetch and initWithBinary. initWithFetch is the default and is recommended for better performance (due to streaming). It needs to be given a URL to request the static binary .wasm file from. The default URL is node_modules/fast-topics/dist/topics.wasm, but if you are using a bundler (like Webpack or Vite), then this probably isn't going to work. You need to provide a URL from your bundler to the file.

Example for Vite:

import {initialiseWasm} from 'fast-topics'
import wasmUrl from 'fast-topics/dist/topics.wasm?url' // note ?url

await initialiseWasm(wasmUrl)

When an import ends with ?url, Vite automatically serves it at a static file, and assigns the URL to the import variable (wasmUrl in this example).

Default works with Snowpack:

import {initialiseWasm} from 'fast-topics'

await initialiseWasm()
// getTopics can now safely be called

The initialisation method can be set seperately to actually invoking it, as shown below:

import {
    getTopics,
    initialiseWasm,
    initWithFetch,
    setInitFunction
} from 'fast-topics'
import wasmUrl from 'fast-topics/dist/topics.wasm?url' // ?url for Vite

setInitFunction(initWithFetch(wasmUrl))

// perform other logic
// when WASM is required, run:
await initialiseWasm()

Using an ArrayBuffer to init WebAssembly

The WASM module can also be initialised by providing an ArrayBuffer, however this is not recommended as it prevents streaming.

import {initialiseWasm} from 'fast-topics'

await fetch("node_modules/fast-topics/dist/topics.wasm")
    .then(r => r.arrayBuffer())
    .then(binary => initialiseWasm(binary))