3. Introduction to Web Backend Using JavaScript

Setting Up a Simple Node.js Server

1. Initialize a Node.js Project:

   npm init -y

2. Install Express:

   npm install express

3. Create a Simple Server:

   • Create server.js:

   const express = require('express');
   const app = express();
   const port = 5000;
   
   app.get('/', (req, res) => {
     res.send('Hello from the backend!');
   });
   
   app.listen(port, () => {
     console.log(`Server running at http://localhost:${port}`);
   });

   • Run the server:

   node server.js

Connecting Backend with GenAI API

1. Install Axios:

   npm install axios

2. Create an Endpoint to Call GenAI:

   • Update server.js:

   const axios = require('axios');
   
   app.post('/chat', async (req, res) => {
     const response = await axios.post('https://api.openai.com/v1/chat/completions', {
       model: 'gpt-3.5-turbo',
       messages: [{ role: 'user', content: req.body.message }],
       temperature: 0.7
     }, {
       headers: {
         'Authorization': `Bearer ${process.env.OPENAI_API_KEY}`,
         'Content-Type': 'application/json'
       }
     });
   
     res.json(response.data);
   });

3. Testing the Endpoint:

   • Use a tool like Postman to send a POST request to http://localhost:5000/chat.