Best Practices

Introduction

Follow these best practices to use Web Storage safely and efficiently.

Guidelines

// Always use JSON.stringify/parse for non-string values
localStorage.setItem('user', JSON.stringify({ name: 'Alice', id: 1 }));
const user = JSON.parse(localStorage.getItem('user'));

// Handle missing keys (returns null)
const data = JSON.parse(localStorage.getItem('missing') || 'null');

// Don't store sensitive data (passwords, tokens, credit cards)
// Web Storage is accessible via JavaScript (XSS vulnerable)

// Limit frequent writes (debounce saves)
const saveSettings = debounce(() => {
  localStorage.setItem('settings', JSON.stringify(settings));
}, 500);

// Catch quota exceeded errors
try {
  localStorage.setItem('key', 'large data...');
} catch (e) {
  if (e.name === 'QuotaExceededError') {
    console.error('Storage full — clear old data');
  }
}

Summary

Do	Don’t
Use JSON for objects	Store sensitive data
Handle null returns	Store large blobs/files
Debounce frequent writes	Assume it’s available (private browsing may block)
Catch quota errors	Store JWTs (use httpOnly cookies)

Best Practices

Best Practices

Introduction

Guidelines

Summary

Further Reading