Chatbots Tutorial

A chatbot is a program that talks with people in text or voice. Businesses use chatbots to answer customer questions on websites and WhatsApp, colleges use them for admission queries, and millions of people chat with AI assistants like ChatGPT, Gemini and Claude every day.

In this tutorial you will learn how chatbots work and build one step by step: first a simple rule-based bot in JavaScript, then a real AI chatbot that calls an AI model from a secure Node.js server.

What You Will Learn

• What chatbots are, and rule-based bots vs AI bots
• How an AI chatbot works behind the scenes
• How to design good conversations
• Building a rule-based bot in JavaScript
• Calling an AI API from a Node.js server, with keys kept secret
• Streaming replies word by word
• Adding your own knowledge with a system prompt and RAG basics
• Safety, manners and staying on topic
• Putting a chatbot on a website

A First Taste

Here is the smallest possible chatbot "brain" in JavaScript:

function reply(message) {
  const text = message.toLowerCase();
  if (text.includes("hello") || text.includes("salam")) return "Walaikum Assalam! How can I help?";
  if (text.includes("timing")) return "We are open 10 am to 8 pm, Monday to Saturday.";
  return "Sorry, I did not understand. Please ask about timings.";
}
console.log(reply("Salam"));
console.log(reply("What are your timings?"));

Walaikum Assalam! How can I help?
We are open 10 am to 8 pm, Monday to Saturday.

By the end of the tutorial, you will replace these fixed rules with a real AI model.

Exercises and Quiz

Every lesson ends with an exercise, and the last lesson is a quiz.

Before and After This Tutorial

You should know basic JavaScript; some Node.js helps too. Learn Prompt Engineering to write better system prompts. After this, build bots that take actions in the AI Agents Tutorial.