Install the SDK

```bash

npm install openai

```

Your First Chat Completion

```javascript

import OpenAI from "openai";

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

const response = await client.chat.completions.create({

model: "gpt-4o-mini",

messages: [{ role: "user", content: "Explain async/await in JavaScript" }],

});

console.log(response.choices[0].message.content);

```

Model Selection

- **gpt-4o-mini** — Cheap, fast, handles most tasks well

- **gpt-4o** — Best multimodal performance, vision support

- **gpt-4.5** — Frontier performance for complex tasks

- **o1/o3** — Extended reasoning for math and science

Function Calling

Structured JSON function calling makes tool integrations reliable:

```javascript

const tools = [{ type: "function", function: { name: "get_weather", parameters: {...} }}];

const result = await client.chat.completions.create({ model: "gpt-4o", messages, tools });

```

Free Tier

$5 free credit on new accounts. API pricing is per-token — use gpt-4o-mini for development.