如何在JavaScript中检测Internet连接是否离线?
当前回答
IE 8将支持window.navigator.onLine属性。
但当然,这对其他浏览器或操作系统没有帮助。考虑到了解Ajax应用程序中的在线/离线状态的重要性,我预计其他浏览器供应商也将决定提供该属性。
在此之前,XHR或Image()或<img>请求都可以提供接近您想要的功能。
更新(2014/11/16)
大多数浏览器现在都支持这个属性,但结果会有所不同。
引用自Mozilla文档:
In Chrome and Safari, if the browser is not able to connect to a local area network (LAN) or a router, it is offline; all other conditions return true. So while you can assume that the browser is offline when it returns a false value, you cannot assume that a true value necessarily means that the browser can access the internet. You could be getting false positives, such as in cases where the computer is running a virtualization software that has virtual ethernet adapters that are always "connected." Therefore, if you really want to determine the online status of the browser, you should develop additional means for checking. In Firefox and Internet Explorer, switching the browser to offline mode sends a false value. All other conditions return a true value.
其他回答
您可以使用$.ajax()的错误回调,它在请求失败时触发。如果textStatus等于字符串"timeout",这可能意味着连接中断:
function (XMLHttpRequest, textStatus, errorThrown) {
// typically only one of textStatus or errorThrown
// will have info
this; // the options for this ajax request
}
医生说:
错误:一个函数被调用,如果请求 失败。函数被传递了3个 参数:XMLHttpRequest对象 描述错误类型的字符串 这是可选的 异常对象,如果发生。 第二个可能的值 参数(除null外)为"timeout", "error", "notmodified"和 “parsererror”。这是一个Ajax事件
例如:
$.ajax({
type: "GET",
url: "keepalive.php",
success: function(msg){
alert("Connection active!")
},
error: function(XMLHttpRequest, textStatus, errorThrown) {
if(textStatus == 'timeout') {
alert('Connection seems dead!');
}
}
});
只需使用导航器。如果这是真的,那么你是在线的,否则离线
HTML5应用程序缓存API指定导航器。onLine,目前在IE8测试版中可用,WebKit(例如。Safari)的夜间运行,并且已经在Firefox 3中得到支持
if(navigator.onLine){
alert('online');
} else {
alert('offline');
}
IE 8将支持window.navigator.onLine属性。
但当然,这对其他浏览器或操作系统没有帮助。考虑到了解Ajax应用程序中的在线/离线状态的重要性,我预计其他浏览器供应商也将决定提供该属性。
在此之前,XHR或Image()或<img>请求都可以提供接近您想要的功能。
更新(2014/11/16)
大多数浏览器现在都支持这个属性,但结果会有所不同。
引用自Mozilla文档:
In Chrome and Safari, if the browser is not able to connect to a local area network (LAN) or a router, it is offline; all other conditions return true. So while you can assume that the browser is offline when it returns a false value, you cannot assume that a true value necessarily means that the browser can access the internet. You could be getting false positives, such as in cases where the computer is running a virtualization software that has virtual ethernet adapters that are always "connected." Therefore, if you really want to determine the online status of the browser, you should develop additional means for checking. In Firefox and Internet Explorer, switching the browser to offline mode sends a false value. All other conditions return a true value.