JavaScript Online_detection Guide
Detect online/offline status with navigator.onLine and online/offline events for offline-first applications. The guide walks through Online Events. `navigator.onLine` — boolean. `window.addEventListener("online",handler)` — back online. `window.addEventListener("offline",handler)` — lost connection. Use: queue failed requests, show offline indicator, sync when back online, switch to cached content. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.