js-cache-storage

localStorage, sessionStorage, and document.cookie are synchronous and expensive. Cache reads in memory.

Skills
Web development
0

What it does and how to use it

A skill that teaches Claude Code to do web development tasks well. It is packaged knowledge the model uses whenever it is relevant.

Install the skill (command above).
In Claude Code, describe what you need - the skill turns on by itself when the context fits.
No commands to memorize: you talk in plain language and the skill does the rest.

Install (Claude Code)

mkdir -p .claude/skills/js-cache-storage && curl -fsSL https://doutorai.pt/data/lib/skills__js-cache-storage.md -o .claude/skills/js-cache-storage/SKILL.md

Paste this command into the terminal, in your project folder, and the component installs automatically.

Content

---
title: Cache Storage API Calls
impact: LOW-MEDIUM
impactDescription: reduces expensive I/O
tags: 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):**

```typescript
function getTheme() {
  return localStorage.getItem('theme') ?? 'light'
}
// Called 10 times = 10 storage reads
```

**Correct (Map cache):**

```typescript
const storageCache = new Map<string, string | null>()

function getLocalStorage(ke

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