XMLHTTPRequest - 測試連接而不是.send（null）失敗

Question

var xml = null; 
    xml = new XMLHttpRequest(); 
    xml.open("get", who, false); 
      xml.send(null); 
    if ((xml.status >= 200 && xml.status <= 300) || xml.status == 304) { 
    var hi = xml.responseText; 
    } else { 
    alert("No Internet Connection! You will have to enter information by hand"); 
    }; 

我想設置此警報，如果沒有互聯網連接，它會這樣說。但是，瀏覽器使用NS_ERROR_FAILURE停止/掛起在xml.send（null）：失敗。如何正確設置連接的測試？

Answer 1

試試這個。

function check() { 
    var z, xml = null; 
    xml = new XMLHttpRequest(); 
    xml.open("get", who, false); 
    try { 
     xml.send(null); 
    } catch(z) { 
     alert("Network failure"); 
     return; 
    } 
    if ((xml.status >= 200 && xml.status <= 300) || xml.status == 304) { 
     var hi = xml.responseText; 
    } else { 
     alert("No Internet Connection! You will have to enter information by hand"); 
    } 
}