<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script> /*1.ononline:网络连通的时候触发这个事件*/ window.addEventListener("online",function(){ alert("网络连通了"); }); /*2.onoffline:网络断开时触发*/ window.addEventListener("offline",function(){ alert("网络断开了"); }) </script> </body> </html>