Search Plugin for Gatsby

    npm install --save gatsby-plugin-lunr

    yarn add gatsby-plugin-lunr

module.exports = {
    plugins: [
        {
            resolve: `gatsby-plugin-lunr`,
            options: {
                languages: [
                    {
                        // ISO 639-1 language codes. See https://lunrjs.com/guides/language_support.html for details
                        name: 'en',
                        // A function for filtering nodes. () => true by default
                        filterNodes: node => node.frontmatter.lang === 'en',
                        // Add to index custom entries, that are not actually extracted from gatsby nodes
                        customEntries: [{ title: 'Pictures', content: 'awesome pictures', url: '/pictures' }],
                    },
                    {
                        name: 'fr',
                        filterNodes: node => node.frontmatter.lang === 'fr',
                    },
                ],
                // Fields to index. If store === true value will be stored in index file.
                // Attributes for custom indexing logic. See https://lunrjs.com/docs/lunr.Builder.html for details
                fields: [
                    { name: 'title', store: true, attributes: { boost: 20 } },
                    { name: 'content' },
                    { name: 'url', store: true },
                ],
                // How to resolve each field's value for a supported node type
                resolvers: {
                    // For any node of type MarkdownRemark, list how to resolve the fields' values
                    MarkdownRemark: {
                        title: node => node.frontmatter.title,
                        content: node => node.rawMarkdownBody,
                        url: node => node.fields.url,
                    },
                },
                //custom index file name, default is search_index.json
                filename: 'search_index.json',
                //custom options on fetch api call for search_ındex.json
                fetchOptions: {
                    credentials: 'same-origin'
                },
            },
        },
    ],
}

const myPlugin = (lunr) => (builder) => {
  // removing stemmer
  builder.pipeline.remove(lunr.stemmer)
  builder.searchPipeline.remove(lunr.stemmer)
  // or similarity tuning
  builder.k1(1.3)
  builder.b(0)
}

import React, { Component } from 'react'

// Search component
export default class Search extends Component {
    constructor(props) {
        super(props)
        this.state = {
            query: ``,
            results: [],
        }
    }

    render() {
        return (
            <div>
                <input type="text" value={this.state.query} onChange={this.search} />
                <ul>{this.state.results.map(page => <li>{page.title}</li>)}</ul>
            </div>
        )
    }

    getSearchResults(query) {
        if (!query || !window.__LUNR__) return []
        const lunrIndex =  window.__LUNR__[this.props.lng];
        const results = lunrIndex.index.search(query) // you can  customize your search , see https://lunrjs.com/guides/searching.html
        return results.map(({ ref }) => lunrIndex.store[ref])
    }

    search = event => {
        const query = event.target.value
        const results = this.getSearchResults(query)
        this.setState(s => {
            return {
                results,
                query,
            }
        })
    }
}