Cache Control in JavaScript

// Cache modes
await fetch(url, {
  cache: 'default'     // Browser decides
})

await fetch(url, {
  cache: 'no-cache'    // Validate with server
})

await fetch(url, {
  cache: 'reload'      // Bypass cache completely
})

await fetch(url, {
  cache: 'force-cache' // Use cache if available
})

await fetch(url, {
  cache: 'only-if-cached' // Cache only, fail otherwise
})

// Cache with headers
const response = await fetch(url, {
  cache: 'no-cache',
  headers: {
    'Cache-Control': 'no-cache',
    'Pragma': 'no-cache'
  }
})

// Conditional requests
const response = await fetch(url, {
  headers: {
    'If-Modified-Since': lastModified,
    'If-None-Match': etag
  }
})

if (response.status === 304) {
  console.log('Not modified, use cached version')
}