HouYunFei
fb79a15508
- 添加 sections 定义文件，包含性能优化各领域分类 - 添加规则模板文件，规范文档结构和标签定义 - 添加异步操作优化规则，包括防止瀑布流、并行化、延迟等待等 - 添加包大小优化规则，包括避免桶式导入、动态导入、预加载等 - 添加服务端性能优化规则，包括 API 路
1.6 KiB
1.6 KiB
title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Cache Storage API Calls | LOW-MEDIUM | reduces expensive I/O | javascript, localStorage, storage, caching, performance |
Cache Storage API Calls
localStorage, sessionStorage, and document.cookie are synchronous and expensive. Cache reads in memory.
Incorrect (reads storage on every call):
function getTheme() {
return localStorage.getItem('theme') ?? 'light'
}
// Called 10 times = 10 storage reads
Correct (Map cache):
const storageCache = new Map<string, string | null>()
function getLocalStorage(key: string) {
if (!storageCache.has(key)) {
storageCache.set(key, localStorage.getItem(key))
}
return storageCache.get(key)
}
function setLocalStorage(key: string, value: string) {
localStorage.setItem(key, value)
storageCache.set(key, value) // keep cache in sync
}
Use a Map (not a hook) so it works everywhere: utilities, event handlers, not just React components.
Cookie caching:
let cookieCache: Record<string, string> | null = null
function getCookie(name: string) {
if (!cookieCache) {
cookieCache = Object.fromEntries(
document.cookie.split('; ').map(c => c.split('='))
)
}
return cookieCache[name]
}
Important (invalidate on external changes):
If storage can change externally (another tab, server-set cookies), invalidate cache:
window.addEventListener('storage', (e) => {
if (e.key) storageCache.delete(e.key)
})
document.addEventListener('visibilitychange', () => {
if (document.visibilityState === 'visible') {
storageCache.clear()
}
})