Nonblocking search using async

[Benjamin-Lee]

Description

Right now, it appears that adding search functionality blocks the UI thread while it runs. While I can move it to a webworker, it would be ideal to just await the results.

Describe the solution you'd like

Use async js when searching a large (10k element) JSON array.

Describe alternatives you've considered

Webworkers?

[cschweda]

+1

Just noticing this now. UI freezes as search is generating.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days

[cschweda]

+1 -- any ideas on this?

[itsadamlove]

+1 also having issues with this

[prithvi2k2]

@krisk is this blocking of io addressed?

[Tamnac]

+1 Can we re-open this issue. Web workers seem a little overkill for a simple search. Would be nice to have some sort of async + cancel functionality

[krisk]

JavaScript is single-threaded — making search() async doesn't make it non-blocking. The computation still has to happen somewhere.

If search is blocking your UI, the real options are:

1. Web Worker — run Fuse in a worker to keep the main thread free. This is a wrapper you set up in your app, not something Fuse should own (worker lifecycle, serialization, message passing are all app-level concerns).
2. Reduce the dataset — pre-filter before searching, or use limit to enable the heap-based fast path.
3. Debounce — don't search on every keystroke.

Fuse is a client-side library for datasets that fit in memory and search in milliseconds. If you're searching millions of records, a server-side engine is the right tool.

[krisk]

Well, turns out Web Workers aren't overkill after all. I take it back.

I've been working on built-in parallel search support via a new FuseWorker class. Instead of running search on the main thread (which blocks the UI), FuseWorker splits your dataset across multiple Web Workers and searches them in parallel.

Usage:

import { FuseWorker } from 'fuse.js/worker'

const fuse = new FuseWorker(docs, options)
const results = await fuse.search('query')
fuse.terminate()

Same options, same results as Fuse — just async. Workers are created lazily on first search, no setup needed.

Benchmarks (100K documents, browser):

Method	Time	Speedup
Fuse (single thread)	6,276ms	1.00x
FuseWorker (2 workers)	3,514ms	1.79x
FuseWorker (4 workers)	1,909ms	3.29x
FuseWorker (8 workers)	1,338ms	4.69x

More importantly, the UI stays completely responsive during search — no jank, no frozen frames.

The API is intentionally small: search, add, setCollection, terminate. If you need to remove items, call setCollection with a filtered array.

Branch: feat/web-workers | Commit: 6e54a1d4

Planning to ship this as a beta release. Feedback welcome — especially on the API surface and whether the worker count defaults make sense for your use cases.