JavaScript判断网络状态的两种核心方法

if (window.navigator.onLine) {
  console.log('网络正常！');
} else {
  console.log('网络中断！');
}

<script type="text/javascript">
  if (window.addEventListener) {  
    window.addEventListener("online", () => {  
      console.log('网络连接恢复');
    }, true);  
    window.addEventListener("offline", () => {  
      console.log('网络连接中断');
    }, true);   
  }else if (window.attachEvent) {  
    window.attachEvent("ononline", () => {  
      console.log('网络连接恢复');
    });  
    window.attachEvent("onoffline", () => {  
      console.log('网络连接中断');
    }); 
  }else {  
    window.ononline = () => {  
      console.log('网络连接恢复');
    };  
    window.onoffline = () => {
      console.log('网络连接中断');
    }; 
  } 
</script>