cursor-hello-world

# Cursor Hello World

A hands-on 10-minute walkthrough of Cursor's four core AI features: Tab Completion, Chat, Inline Edit, and Composer.

## Setup

```bash
mkdir cursor-hello && cd cursor-hello
npm init -y
npm install typescript tsx @types/node --save-dev
npx tsc --init
```

Open the project in Cursor: `cursor .` (or File > Open Folder).

## Exercise 1: Tab Completion

Create `src/utils.ts`. Start typing and let Tab complete:

```typescript
// Type this much:
export function formatCurrency(amount: number, currency: string

// Tab suggests:
export function formatCurrency(amount: number, currency: string = 'USD'): string {
  return new Intl.NumberFormat('en-US', {
    style: 'currency',
    currency,
  }).format(amount);
}
```

Press **Tab** to accept the full suggestion, or **Cmd+Right Arrow** to accept word-by-word.

### Try These Prompts for Tab

Type a comment describing what you want, then start the function:

```typescript
// Validate an email address using regex
export function validateEmail(

// Sort an array of objects by a key
export function sortBy<T>(

// Calculate the distance between two lat/lng points in km
export function haversineDistance(
```

Tab reads your comment and generates the implementation.

## Exercise 2: Chat (Cmd+L)

Open Chat with `Cmd+L`. Try these prompts:

**Ask about your code:**
```
@src/utils.ts
What does the formatCurrency function do? Does it handle edge cases
like negative numbers or very large values?
```

**Generate new code:**
```
Write a TypeScript function that converts a nested object
to a flat key-value map with dot-separated keys.
Example: { a: { b: 1 } } → { "a.b": 1 }
```

**Debug a concept:**
```
Explain the difference between Promise.all() and Promise.allSettled()
with code examples showing when to use each.
```

Chat responds with explanations and code snippets. Click **Apply** on any code block to insert it into your editor.

## Exercise 3: Inline Edit (Cmd+K)

Open `src/utils.ts`. Select the `formatCurrency` function body. Press `Cmd+K`.

Type your instruction:
```
Add support for locale parameter with default 'en-US'.
Handle NaN input by returning '$0.00'.
```

Cursor shows the diff inline:
- Green = added lines
- Red = removed lines

Press `Cmd+Y` to accept, `Esc` to reject.

### Inline Edit Quick Tasks

Select any code and press `Cmd+K` with instructions like:
- `"Add TypeScript types"`
- `"Refactor to use early returns"`
- `"Add error handling"`
- `"Convert to async/await"`
- `"Add JSDoc documentation"`

## Exercise 4: Composer (Cmd+I)

Press `Cmd+I` to open Composer. Ask it to create a complete feature:

```
Create a simple task manager module:

1. src/types/task.ts - Task interface with id, title, completed, createdAt
2. src/services/task-service.ts - TaskService class with:
   - addTask(title: string): Task
   - completeTask(id: string): Task
   - listTasks(): Task[]
   - deleteTask(id: string): void
3. src/index.ts - Demo script that creates 3 tasks, completes one, lists all

Use in-memory storage (Map). Include TypeScript types throughout.
```

Composer shows all files it will create/modify. Review each diff, then click **Apply All**.

### Run the Result

```bash
npx tsx src/index.ts
```

## Feature Comparison Summary

| Feature | Shortcut | Use For | Scope |
|---------|----------|---------|-------|
| **Tab** | Automatic | Line/block completions while typing | Current cursor position |
| **Chat** | `Cmd+L` | Questions, explanations, code snippets | Conversation-based |
| **Inline Edit** | `Cmd+K` | Edit selected code with instructions | Selected code block |
| **Composer** | `Cmd+I` | Multi-file generation and refactoring | Multiple files |

## Next Steps After Hello World

1. **Add project rules**: Create `.cursor/rules/` with coding standards (see cursor-rules-config skill)
2. **Index your codebase**: Open a real project and wait for indexing (see cursor-codebase-indexing skill)
3. **Learn @-mentions**: Use `@Files`, `@Codebase`, `@Docs` in Chat (see cursor-context-management skill)
4. **Configure your model**: Try different models for different tasks (see cursor-model-selection skill)

## Enterprise Considerations

- Hello World exercises do not send sensitive code to AI providers -- safe for evaluation
- Enable Privacy Mode before using Cursor with production codebases
- Tab completions work immediately; Chat and Composer require active subscription or BYOK API key

## Resources

- [Cursor Getting Started](https://docs.cursor.com/get-started/overview)
- [Cursor Keyboard Shortcuts](https://docs.cursor.com/kbd)
- [Cursor Feature Overview](https://cursor.com/features)