Table of Contents

1. Getting Started
2. Installation and Setup
3. Basic Usage
4. Advanced Features
5. Best Practices
6. Error Handling

Getting Started

Prerequisites

• Node.js (v18+)
• npm or yarn
• An OpenAI account
• API key from OpenAI platform

Project Setup

First, create a new Node.js project:

mkdir openai-project
cd openai-project
npm init -y

Installation and Setup

Install the OpenAI package:

npm install openai dotenv

Create a .env file for your API key:

OPENAI_API_KEY=your-api-key-here

Create an index.js file with the basic setup:

require('dotenv').config();
const OpenAI = require('openai');

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

Basic Usage

Making Your First API Call

async function quickStart() {
  try {
    const completion = await openai.chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: [
        { role: "user", content: "Hello, how can you help me today?" }
      ],
    });

    console.log(completion.choices[0].message.content);
  } catch (error) {
    console.error('Error:', error);
  }
}

quickStart();

Different Types of Requests

// Chat completion with system message
async function chatWithSystem() {
  try {
    const completion = await openai.chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: [
        { role: "system", content: "You are a helpful assistant." },
        { role: "user", content: "What's the weather like?" }
      ],
      temperature: 0.7,
      max_tokens: 150
    });

    console.log(completion.choices[0].message.content);
  } catch (error) {
    console.error('Error:', error);
  }
}

// Image generation
async function generateImage() {
  try {
    const response = await openai.images.generate({
      model: "dall-e-3",
      prompt: "A sunset over mountains",
      size: "1024x1024",
      quality: "standard",
      n: 1,
    });

    console.log(response.data[0].url);
  } catch (error) {
    console.error('Error:', error);
  }
}

Advanced Features

Managing Conversations

class ConversationManager {
  constructor() {
    this.messages = [
      { role: "system", content: "You are a helpful assistant." }
    ];
  }

  async sendMessage(userMessage) {
    try {
      // Add user message to conversation
      this.messages.push({ role: "user", content: userMessage });

      // Get response from API
      const completion = await openai.chat.completions.create({
        model: "gpt-3.5-turbo",
        messages: this.messages
      });

      const assistantResponse = completion.choices[0].message.content;
      
      // Add assistant response to conversation
      this.messages.push({ role: "assistant", content: assistantResponse });

      return assistantResponse;
    } catch (error) {
      console.error('Error:', error);
      throw error;
    }
  }

  getConversationHistory() {
    return this.messages;
  }
}

// Usage example:
const conversation = new ConversationManager();
async function demo() {
  await conversation.sendMessage("Hi there!");
  await conversation.sendMessage("What can you help me with?");
  console.log(conversation.getConversationHistory());
}

Stream Responses

async function streamCompletion() {
  try {
    const stream = await openai.chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: [{ role: "user", content: "Write a story about a dragon" }],
      stream: true,
    });

    for await (const chunk of stream) {
      const content = chunk.choices[0]?.delta?.content || '';
      process.stdout.write(content);
    }
  } catch (error) {
    console.error('Error:', error);
  }
}

Best Practices

Rate Limiting and Batching

class RateLimiter {
  constructor(requestsPerMinute) {
    this.requestsPerMinute = requestsPerMinute;
    this.queue = [];
    this.processing = false;
  }

  async addRequest(prompt) {
    return new Promise((resolve, reject) => {
      this.queue.push({ prompt, resolve, reject });
      if (!this.processing) {
        this.processQueue();
      }
    });
  }

  async processQueue() {
    this.processing = true;
    while (this.queue.length > 0) {
      const { prompt, resolve, reject } = this.queue.shift();
      try {
        const response = await openai.chat.completions.create({
          model: "gpt-3.5-turbo",
          messages: [{ role: "user", content: prompt }]
        });
        resolve(response.choices[0].message.content);
      } catch (error) {
        reject(error);
      }
      // Wait for rate limit
      await new Promise(resolve => setTimeout(resolve, (60 / this.requestsPerMinute) * 1000));
    }
    this.processing = false;
  }
}

// Usage
const limiter = new RateLimiter(60); // 60 requests per minute
const prompts = ["Hello", "How are you", "What's the weather"];
Promise.all(prompts.map(prompt => limiter.addRequest(prompt)))
  .then(responses => console.log(responses));

Error Handling

class OpenAIHandler {
  constructor() {
    this.maxRetries = 3;
    this.baseDelay = 1000; // 1 second
  }

  async makeRequest(prompt, retryCount = 0) {
    try {
      const response = await openai.chat.completions.create({
        model: "gpt-3.5-turbo",
        messages: [{ role: "user", content: prompt }]
      });
      return response.choices[0].message.content;
    } catch (error) {
      if (retryCount < this.maxRetries) {
        const delay = this.baseDelay * Math.pow(2, retryCount);
        console.log(`Retrying after ${delay}ms...`);
        await new Promise(resolve => setTimeout(resolve, delay));
        return this.makeRequest(prompt, retryCount + 1);
      }
      throw error;
    }
  }
}

Cost Management

const GPT3Tokenizer = require('gpt3-tokenizer').default;

class TokenCounter {
  constructor() {
    this.tokenizer = new GPT3Tokenizer({ type: 'gpt3' });
  }

  countTokens(text) {
    const encoded = this.tokenizer.encode(text);
    return encoded.bpe.length;
  }

  estimateCost(tokens, model = 'gpt-3.5-turbo') {
    const costs = {
      'gpt-3.5-turbo': 0.002 / 1000,
      'gpt-4': 0.03 / 1000,
    };
    return tokens * costs[model];
  }
}

// Usage tracking middleware
function trackUsage(response) {
  const usage = response.usage;
  console.log({
    promptTokens: usage.prompt_tokens,
    completionTokens: usage.completion_tokens,
    totalTokens: usage.total_tokens,
    estimatedCost: new TokenCounter().estimateCost(usage.total_tokens)
  });
}

Remember to:

1. Never commit your .env file
2. Use appropriate error handling in production
3. Implement proper rate limiting
4. Monitor your token usage and costs
5. Keep your API key secure
6. Use environment variables for sensitive data