# Lunr.js — Full-Text Search Engine for the Browser

> A small full-text search library for client-side applications, providing stemming, field boosting, and wildcard queries in an index you build once and query instantly.

## Install

Save in your project root:

# Lunr.js — Full-Text Search Engine for the Browser

## Quick Use
```bash
npm install lunr
```
```js
const lunr = require('lunr');
const idx = lunr(function () {
  this.field('title');
  this.field('body');
  this.add({id: 1, title: 'Intro', body: 'Welcome to Lunr'});
});
console.log(idx.search('lunr'));
```

## Introduction
Lunr.js is a small, full-text search library for use in the browser and Node.js. Inspired by Solr, it provides a simple way to build a search index over your documents and query it with features like stemming, boosting, and wildcards, all without external services.

## What Lunr.js Does
- Builds a full-text search index from JavaScript objects with configurable fields
- Supports stemming, stop word removal, and language-specific text processing
- Enables field boosting to prioritize matches in specific document fields
- Provides wildcard, fuzzy matching, and term presence/absence operators
- Serializes indexes to JSON for pre-building at compile time and loading at runtime

## Architecture Overview
Lunr.js constructs an inverted index during the build phase, tokenizing and stemming each document field into terms that map to document references. The index uses a trie-based structure for efficient prefix and wildcard lookups. At query time, the search engine resolves each query clause against the index, scores matches using TF-IDF with optional field boosts, and returns sorted results.

## Self-Hosting & Configuration
- Install via npm or include via a script tag from a CDN
- Define an index inside the lunr callback, specifying fields and adding documents
- Set field boosts with this.field(name, {boost: N}) to weight certain fields higher
- Pre-build the index server-side and serialize with JSON.stringify for faster client-side loading
- Add language support via lunr-languages plugin packs for stemming and stop words

## Key Features
- Zero dependencies and works identically in Node.js and browsers
- Pre-built index serialization to JSON for static sites and documentation
- Language support for 14+ languages via community stemmer plugins
- Query syntax with wildcards, fuzzy matches, boosts, and required/prohibited terms
- Pipeline-based text processing that is customizable with user-defined functions

## Comparison with Similar Tools
- **Fuse.js** — fuzzy search without indexing; better for small datasets, no stemming or field boosting
- **FlexSearch** — faster for very large datasets with context-based scoring; less standard query syntax
- **MiniSearch** — similar API with auto-suggest and prefix search; actively maintained alternative
- **Algolia** — hosted search-as-a-service with dashboards and analytics; requires a server and API key

## FAQ
**Q: Can I update the index after building it?**
A: No, Lunr indexes are immutable once built. Rebuild the index when your data changes.

**Q: How large a dataset can Lunr handle?**
A: It works well for up to tens of thousands of documents. Larger datasets may cause slow build times or high memory use.

**Q: Can I use Lunr with TypeScript?**
A: Yes, type definitions are available via @types/lunr on npm.

**Q: How do I search across multiple fields at once?**
A: All indexed fields are searched by default. Use field-prefixed queries like title:keyword to restrict to a specific field.

## Sources
- https://github.com/olivernn/lunr.js
- https://lunrjs.com/

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Source: https://tokrepo.com/en/workflows/asset-2e5b7aff
Author: AI Open Source