# CHAPTER 3 SUMMARY

## Key Concepts Introduced
1. **Query Parameters** - params option for automatic encoding - Used in chapters: 4, 7, 8, 9, 10
2. **Headers in Detail** - Authorization, Accept, custom headers - Used in chapters: 4, 8, 10
3. **Pagination Patterns** - Page-based and generator patterns - Used in chapters: 10, 13
4. **Polling for Real-time** - setInterval with cleanup - Used in chapters: 9
5. **Parallel Requests** - Promise.all() for performance - Used in chapters: 10, 13
6. **Conditional Requests** - ETags and If-None-Match - Used in chapters: 6, 10
7. **Request Interceptors** - Setting default headers - Used in chapters: 8
8. **Response Transformation** - addResponseInterceptor - Used in chapters: 8

## Code Patterns Established
```javascript
// Pattern 1: Query parameters
const { data } = await tf.get(url, {
  params: { key: 'value' }
})

// Pattern 2: Headers
const { data } = await tf.get(url, {
  headers: { 'Authorization': 'Bearer token' }
})

// Pattern 3: Parallel requests
const [a, b, c] = await Promise.all([
  tf.get(url1),
  tf.get(url2),
  tf.get(url3)
])

// Pattern 4: Pagination with generators
async function* fetchPages() {
  let page = 1
  while (hasMore) {
    const { data } = await tf.get(url, { params: { page } })
    yield* data.items
    hasMore = data.hasNext
    page++
  }
}
```

## API Endpoints Used
- api.teleport.org/api/cities/ - City search with autocomplete
- wttr.in/{city}?format=j1 - Weather data JSON format
- api.github.com/user/repos - GitHub repositories (auth example)
- api.github.com/search/repositories - GitHub search API

## Advanced Patterns Introduced
1. **Debouncing** - Search with 300ms delay
2. **Error Recovery** - Consecutive error counting
3. **Request Signing** - AWS-style signatures
4. **GraphQL via GET** - Query in params
5. **Custom Instances** - createTypedFetch()

## Building Blocks for Next Chapter
- Learned: Reading data with GET
- Mastered: Headers and parameters
- Ready for: Creating/updating data with POST/PUT/DELETE

## Weather Buddy App Status
- Version 3.0: Multi-city dashboard
- Features: Live search, auto-complete, polling updates
- Added: Add/remove cities, error recovery
- Next: Save preferences, share dashboards (Chapter 4)

## Performance Tips Given
1. Use parallel requests over sequential
2. Request only needed fields
3. Implement proper pagination
4. Use conditional requests with ETags
5. Cache responses (automatic with TypedFetch)

## Debug Features Shown
```javascript
tf.enableDebug()
// Shows request details, timing, caching info
```