Basic Search Engine with Node.js and Express

Creating a basic search engine with Node.js and Express involves setting up a search index, implementing search functionality, and displaying search results. Below is a step-by-step guide to help you build a simple search engine.

Step 1: Set Up Your Project

Create a new project folder:
```
 mkdir search-engine
 cd search-engine
```
Initialize a new Node.js project:
```
 npm init -y
```
Install necessary dependencies:
```
 npm install express ejs lunr
```

Step 2: Create Your Folder Structure

Create the following folder structure:

search-engine/
|-- src/
|   |-- views/
|       |-- index.ejs
|   |-- routes/
|       |-- search.js
|   |-- data/
|       |-- sample-data.json
|   |-- app.js
|-- server.js
|-- .gitignore
|-- package.json

Step 3: Set Up Express Server

In app.js, set up an Express server:

const express = require('express');
const path = require('path');
const searchRoutes = require('./routes/search');

const app = express();
const PORT = process.env.PORT || 3000;

app.set('view engine', 'ejs');
app.use(express.static(path.join(__dirname, 'public')));

// Routes
app.use('/search', searchRoutes);

app.listen(PORT, () => {
  console.log(`Server is running on http://localhost:${PORT}`);
});

Step 4: Create Search Routes

In routes/search.js, set up routes for handling search functionality:

const express = require('express');
const router = express.Router();
const lunr = require('lunr');
const fs = require('fs');
const path = require('path');

const dataPath = path.join(__dirname, '../data/sample-data.json');

// Load sample data
const rawData = fs.readFileSync(dataPath, 'utf-8');
const sampleData = JSON.parse(rawData);

// Create Lunr index
const searchIndex = lunr(function () {
  this.ref('id');
  this.field('title');
  this.field('content');

  sampleData.forEach(function (item, index) {
    item.id = index;
    this.add(item);
  }, this);
});

router.get('/', (req, res) => {
  const query = req.query.q;
  let results = [];

  if (query) {
    results = searchIndex.search(query).map(result => sampleData[result.ref]);
  }

  res.render('index', { query, results });
});

module.exports = router;

Step 5: Create Views

In views/, create the following EJS template:

index.ejs: Display the main page with a search form and search results.

Step 6: Create Main Page

In views/index.ejs, create the main page:

<!-- views/index.ejs -->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Search Engine</title>
</head>
<body>
  <h1>Search Engine</h1>
  <form action="/search" method="get">
    <label for="searchQuery">Search:</label>
    <input type="text" id="searchQuery" name="q" value="<%= query %>" required>
    <button type="submit">Search</button>
  </form>

  <% if (results.length > 0) { %>
    <h2>Search Results</h2>
    <ul>
      <% results.forEach(result => { %>
        <li>
          <h3><%= result.title %></h3>
          <p><%= result.content %></p>
        </li>
      <% }); %>
    </ul>
  <% } else if (query) { %>
    <p>No results found for "<%= query %>".</p>
  <% } %>
</body>
</html>

Step 7: Create Sample Data

In data/sample-data.json, create sample data for indexing and searching:

[
  {
    "title": "Introduction to Node.js",
    "content": "Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine.",
    "tags": ["Node.js", "JavaScript"]
  },
  {
    "title": "Express.js Basics",
    "content": "Express.js is a minimal and flexible Node.js web application framework.",
    "tags": ["Express.js", "Node.js"]
  },
  {
    "title": "Web Development with HTML and CSS",
    "content": "Learn the basics of building web pages using HTML and CSS.",
    "tags": ["HTML", "CSS", "Web Development"]
  }
]

Step 8: Run Your Application

In server.js, use the exported app to start the application:

const app = require('./src/app');

const PORT = process.env.PORT || 3000;

app.listen(PORT, () => {
  console.log(`Server is running on http://localhost:${PORT}`);
});

Start the server:

node server.js

Visit http://localhost:3000/search in your browser to see and interact with your search engine. Enter a search query in the form and click the "Search" button to see the search results.

Congratulations! You've successfully created a basic search engine using Node.js, Express, and the Lunr library for indexing and searching. Customize and expand this application based on your specific requirements.