Cursor rule

1---
2alwaysApply: false
3---
4 
5## Version and Minimize localStorage Data
6 
7Add version prefix to keys and store only needed fields. Prevents schema conflicts and accidental storage of sensitive data.
8 
9**Incorrect:**
10 
11```typescript
12// No version, stores everything, no error handling
13localStorage.setItem('userConfig', JSON.stringify(fullUserObject))
14const data = localStorage.getItem('userConfig')
15```
16 
17**Correct:**
18 
19```typescript
20const VERSION = 'v2'
21 
22function saveConfig(config: { theme: string; language: string }) {
23  try {
24    localStorage.setItem(`userConfig:${VERSION}`, JSON.stringify(config))
25  } catch {
26    // Throws in incognito/private browsing, quota exceeded, or disabled
27  }
28}
29 
30function loadConfig() {
31  try {
32    const data = localStorage.getItem(`userConfig:${VERSION}`)
33    return data ? JSON.parse(data) : null
34  } catch {
35    return null
36  }
37}
38 
39// Migration from v1 to v2
40function migrate() {
41  try {
42    const v1 = localStorage.getItem('userConfig:v1')
43    if (v1) {
44      const old = JSON.parse(v1)
45      saveConfig({ theme: old.darkMode ? 'dark' : 'light', language: old.lang })
46      localStorage.removeItem('userConfig:v1')
47    }
48  } catch {}
49}
50```
51 
52**Store minimal fields from server responses:**
53 
54```typescript
55// User object has 20+ fields, only store what UI needs
56function cachePrefs(user: FullUser) {
57  try {
58    localStorage.setItem('prefs:v1', JSON.stringify({
59      theme: user.preferences.theme,
60      notifications: user.preferences.notifications
61    }))
62  } catch {}
63}
64```
65 
66**Always wrap in try-catch:** `getItem()` and `setItem()` throw in incognito/private browsing (Safari, Firefox), when quota exceeded, or when disabled.
67 
68**Benefits:** Schema evolution via versioning, reduced storage size, prevents storing tokens/PII/internal flags.
69