2nd/10_Wiki/Topics/Frontend/Throttling Debouncing.md

---
id: wiki-2026-0508-throttling-debouncing
title: Throttling Debouncing
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Throttle, Debounce, Rate Limiting Frontend]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [frontend, performance, event-handling, javascript]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: typescript
  framework: vanilla
---

# Throttling Debouncing

## 매 한 줄
> **"매 throttle 의 rate-limit, debounce 의 quiet-period wait"**. 두 기법 모두 high-frequency event (scroll/resize/input/keypress) 의 handler call 빈도를 줄이지만, semantics 가 정반대 — throttle 의 every N ms 1 call, debounce 의 last call after N ms idle.

## 매 핵심

### 매 Throttle
- **Semantic**: max 1 call per interval.
- **Use**: scroll, resize, mousemove — continuous events 의 sampling.
- **Variants**: leading (immediate first), trailing (last in window), both.
- **Visualizable**: `XX_XX_XX_XX_X` (regular ticks).

### 매 Debounce
- **Semantic**: 1 call after last invocation + delay (no calls during burst).
- **Use**: search input, form validate, autocomplete, window-resize-finish.
- **Variants**: leading (immediate, then ignore), trailing (default), maxWait (force flush).
- **Visualizable**: `XXX____X` (settles after burst).

### 매 응용
1. Search-as-you-type: debounce 300ms.
2. Infinite scroll trigger: throttle 100ms.
3. Auto-save: debounce 1s with maxWait 10s.

## 💻 패턴

### Basic debounce (trailing)
```typescript
function debounce<T extends (...args: any[]) => void>(
  fn: T,
  ms: number
): (...args: Parameters<T>) => void {
  let t: ReturnType<typeof setTimeout> | null = null;
  return (...args) => {
    if (t) clearTimeout(t);
    t = setTimeout(() => fn(...args), ms);
  };
}

// Usage
const onSearch = debounce((q: string) => fetchResults(q), 300);
input.addEventListener('input', e => onSearch((e.target as HTMLInputElement).value));
```

### Basic throttle (leading + trailing)
```typescript
function throttle<T extends (...args: any[]) => void>(
  fn: T,
  ms: number
): (...args: Parameters<T>) => void {
  let last = 0;
  let t: ReturnType<typeof setTimeout> | null = null;
  let lastArgs: Parameters<T> | null = null;
  return (...args) => {
    const now = Date.now();
    const remaining = ms - (now - last);
    lastArgs = args;
    if (remaining <= 0) {
      if (t) { clearTimeout(t); t = null; }
      last = now;
      fn(...args);
    } else if (!t) {
      t = setTimeout(() => {
        last = Date.now();
        t = null;
        if (lastArgs) fn(...lastArgs);
      }, remaining);
    }
  };
}
```

### Debounce with cancel + flush
```typescript
function debounceAdv<T extends (...args: any[]) => void>(fn: T, ms: number) {
  let t: ReturnType<typeof setTimeout> | null = null;
  let lastArgs: Parameters<T> | null = null;
  const debounced = (...args: Parameters<T>) => {
    lastArgs = args;
    if (t) clearTimeout(t);
    t = setTimeout(() => { fn(...lastArgs!); t = null; }, ms);
  };
  debounced.cancel = () => { if (t) { clearTimeout(t); t = null; } };
  debounced.flush = () => {
    if (t && lastArgs) { clearTimeout(t); fn(...lastArgs); t = null; }
  };
  return debounced;
}
```

### React hook: useDebouncedValue
```typescript
import { useEffect, useState } from 'react';

export function useDebouncedValue<T>(value: T, ms = 300): T {
  const [v, setV] = useState(value);
  useEffect(() => {
    const t = setTimeout(() => setV(value), ms);
    return () => clearTimeout(t);
  }, [value, ms]);
  return v;
}

// Usage
function Search() {
  const [q, setQ] = useState('');
  const debounced = useDebouncedValue(q, 300);
  useEffect(() => { if (debounced) fetchResults(debounced); }, [debounced]);
  return <input value={q} onChange={e => setQ(e.target.value)} />;
}
```

### rAF throttle (60fps cap)
```typescript
function rafThrottle<T extends (...args: any[]) => void>(fn: T) {
  let scheduled = false;
  let lastArgs: Parameters<T>;
  return (...args: Parameters<T>) => {
    lastArgs = args;
    if (scheduled) return;
    scheduled = true;
    requestAnimationFrame(() => {
      fn(...lastArgs);
      scheduled = false;
    });
  };
}

// Best for scroll/resize on 60-120hz displays
window.addEventListener('scroll', rafThrottle(() => updatePosition()));
```

### lodash equivalents
```typescript
import { debounce, throttle } from 'lodash-es';

const onResize = throttle(handleResize, 200, { leading: true, trailing: true });
const onSearch = debounce(handleSearch, 300, { maxWait: 1000 });

// Cleanup on unmount
useEffect(() => () => { onResize.cancel(); onSearch.cancel(); }, []);
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Search input | debounce 200-400ms |
| Scroll handler (positional) | rAF throttle |
| Resize end detection | debounce 150ms |
| Auto-save | debounce 1s + maxWait 10s |
| Rate-limited API call | throttle (leading) |
| Button double-click guard | debounce leading-only |

**기본값**: lodash `debounce`/`throttle` for non-trivial cases; rAF throttle for animation-tied work; useDebouncedValue hook for React inputs.

## 🔗 Graph
- 부모: [[Event Handling]] · [[Frontend Performance]]
- 변형: [[Rate Limiting]] · [[Backpressure]]
- 응용: [[Infinite Scroll]]
- Adjacent: [[requestAnimationFrame]] · [[Web Worker (웹 워커)|Web Workers]] · [[Reactive Streams]]

## 🤖 LLM 활용
**언제**: input handler optimization, scroll/resize perf, rate-limiting UI events.
**언제 X**: server-side rate limiting (use token bucket / Redis), animation timing (use rAF directly).

## ❌ 안티패턴
- **Debounce on click button**: user feels lag; use throttle leading-only.
- **No cleanup on unmount**: timer fires on unmounted component → setState warning / leak.
- **Throttle 16ms manually**: use rAF throttle — sync to display refresh.
- **Debounce without maxWait on auto-save**: user types continuously → never saves.
- **Inline `() => debounce(fn, 300)` in render**: new function each render, debouncing breaks.

## 🧪 검증 / 중복
- Verified (lodash docs, MDN event handling, React docs useDeferredValue/useTransition equivalence).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full canonical (debounce/throttle/rAF/React hook + lodash) |