2nd/10_Wiki/Topics/Frontend/Bundle Size Optimization.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-bundle-size-optimization	Bundle Size Optimization	10_Wiki/Topics	verified	self	JS Bundle Optimization Web Bundle Reduction	none	A	0.9	applied	bundle performance webpack vite tree-shaking		2026-05-10	pending	language framework JavaScript/TypeScript Vite/Rollup/Webpack

Bundle Size Optimization

매 한 줄

"매 byte 매 less 매 user time 매 less". Bundle size optimization은 production JS/CSS payload를 줄여 LCP/INP/TBT 개선 + mobile-first user 의 perceived speed 개선. 2026 standard tooling: Vite + Rollup tree-shaking, modern bundle analysis (Bundle Buddy, esbuild-visualizer), bundle budgets enforcement.

매 핵심

매 4 lever

• Tree shaking: ESM only, sideEffects:false, no re-export wildcards.
• Code splitting: route / component lazy import.
• Compression: brotli > gzip; precompress at build.
• Dependency surgery: heavy lib → lighter alt or self-implement.

매 측정 우선

• Bundle visualizer (rollup-plugin-visualizer, source-map-explorer).
• Bundle budget in CI (e.g., size-limit, bundlesize).
• Real device testing (slow 3G profile).

매 응용

1. Lazy-load route chunks.
2. Remove unused locales (date-fns, moment).
3. Replace lodash with native / lodash-es.

💻 패턴

Vite + visualizer

// vite.config.ts
import { defineConfig } from 'vite';
import { visualizer } from 'rollup-plugin-visualizer';

export default defineConfig({
  plugins: [
    visualizer({ filename: 'stats.html', gzipSize: true, brotliSize: true })
  ],
  build: {
    rollupOptions: {
      output: {
        manualChunks: {
          react: ['react', 'react-dom'],
          vendor: ['date-fns', 'zustand']
        }
      }
    }
  }
});

Route-level code split (React)

import { lazy, Suspense } from 'react';
const Dashboard = lazy(() => import('./Dashboard'));

<Suspense fallback={<Skeleton />}>
  <Dashboard />
</Suspense>

Dynamic import for rare path

async function exportToPDF(data: Item[]) {
  const { jsPDF } = await import('jspdf');
  const doc = new jsPDF();
  doc.text(JSON.stringify(data), 10, 10);
  doc.save('out.pdf');
}

Replace heavy lib

// X moment (~290KB)
import moment from 'moment';
moment().format('YYYY-MM-DD');

// O Intl (built-in, 0KB)
new Intl.DateTimeFormat('en-CA').format(new Date());

// O date-fns/format (tree-shakeable, ~3KB)
import { format } from 'date-fns/format';
format(new Date(), 'yyyy-MM-dd');

sideEffects flag

// package.json — library author 측
{
  "name": "my-lib",
  "type": "module",
  "sideEffects": false,
  "exports": {
    ".": {
      "import": "./dist/index.mjs",
      "types": "./dist/index.d.ts"
    }
  }
}

size-limit budget enforcement

// package.json
{
  "scripts": {
    "size": "size-limit"
  },
  "size-limit": [
    { "path": "dist/index.js", "limit": "50 KB" },
    { "path": "dist/vendor.js", "limit": "120 KB" }
  ]
}

Compression at build (brotli)

import compression from 'vite-plugin-compression2';

export default defineConfig({
  plugins: [
    compression({ algorithm: 'brotliCompress', exclude: [/\.(br)$/, /\.(gz)$/] })
  ]
});

Server: strip locales from dayjs

import dayjs from 'dayjs';
import 'dayjs/locale/ko'; // 매 필요한 것만
dayjs.locale('ko');

매 결정 기준

상황	Approach
Initial bundle > 200KB	route split + lazy load
Single heavy lib	replace 또는 dynamic import
Multi-tenant build	per-tenant treeshake config
Library publish	ESM + sideEffects:false
Edge runtime	bundle ≤ 1MB 가까이 strict budget

기본값: measure first → split → compress → swap heavy deps.

🔗 Graph

• 부모: Frontend Performance
• 변형: Code Splitting
• 응용: Core Web Vitals Optimization (INP, LCP, CLS) · LCP
• Adjacent: Vite · Rollup · esbuild

🤖 LLM 활용

언제: webpack/vite config audit, lib alternative suggestion, bundle analyzer interpretation. 언제 X: 매 production 매 swap deploy — actual measurement 필수.

❌ 안티패턴

• CommonJS lib import: tree shaking blocked — ESM 사용.
• import * as foo: bundler 매 mark 매 모든 export used.
• Polyfill 전체: target browser baseline + browserslist으로 narrow.
• Single chunk all: SPA → 매 long initial — split per route.
• Dev source maps in prod: ship source map only via separate URL or skip.

🧪 검증 / 중복

• Verified (web.dev bundle size guide, Vite docs, size-limit GitHub).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — bundle optim 4 lever + Vite/size-limit pattern