ChatGPT Complete Guide 2026

const OpenAI = require('openai');

const openai = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY, // Store in .env file
});

async function chatWithGPT(message) {
  const completion = await openai.chat.completions.create({
    model: "gpt-4", // or "gpt-3.5-turbo" for faster/cheaper
    messages: [
      { role: "system", content: "You are a helpful assistant." },
      { role: "user", content: message }
    ],
    temperature: 0.7,
    max_tokens: 1000,
  });

  return completion.choices[0].message.content;
}

// Usage
chatWithGPT("Explain quantum computing in simple terms")
  .then(response => console.log(response));

from openai import OpenAI
import os

client = OpenAI(api_key=os.getenv("OPENAI_API_KEY"))

def chat_with_gpt(message):
    response = client.chat.completions.create(
        model="gpt-4",
        messages=[
            {"role": "system", content": "You are a helpful assistant."},
            {"role": "user", "content": message}
        ],
        temperature=0.7,
        max_tokens=1000
    )
    return response.choices[0].message.content

# Usage
response = chat_with_gpt("Explain quantum computing in simple terms")
print(response)

// Express.js API endpoint example
const express = require('express');
const OpenAI = require('openai');
const app = express();

const openai = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY
});

app.post('/api/chat', async (req, res) => {
  try {
    const { message } = req.body;
    
    const completion = await openai.chat.completions.create({
      model: "gpt-4",
      messages: [
        { role: "user", content: message }
      ]
    });

    res.json({ 
      response: completion.choices[0].message.content 
    });
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

app.listen(3000);