如何捕获涉及XmlHttpRequest的错误？

Question

当我通过XMLHttpRequest发送数据到服务器时，我想在TRY {} CATCH（）{}的帮助下捕获所有错误。

如何接收所有错误，例如net::ERR_INTERNET_DISCONNECTED等？

Answer 1

转寄此，

function createXMLHttpRequestObject() 
{ 
    // xmlHttp will store the reference to the XMLHttpRequest object 
    var xmlHttp; 
    // try to instantiate the native XMLHttpRequest object 
    try 
    { 
    // create an XMLHttpRequest object 
    xmlHttp = new XMLHttpRequest(); 
    } 
    catch(e) 
    { 
     try 
    { 
     xmlHttp = new ActiveXObject("Microsoft.XMLHttp"); 
    } 
    catch(e) { } 
    } 
    // return the created object or display an error message 
    if (!xmlHttp) 
    alert("Error creating the XMLHttpRequest object."); 
    else 
    return xmlHttp; 
} 

Answer 2

你应该把所有你认为会导致try块异常的语句。之后，你可以给出几个catch语句 - 每个例外。最后，你可以最后给出 - 这个语句将在Try块之后执行，不管异常是否被抛出或被捕获。

语法可以是这样的：

try{ 
try_statements 
} 

[catch (exception_var_2) { catch_statements_1 }] 
[catch (exception_var_2) { catch_statements_2 }] 
... 
[catch (exception_var_2) { catch_statements_N }] 

[finally { finally_statements }] 

例子：

try { 
    myroutine(); // may throw three exceptions 
} catch (e if e instanceof TypeError) { 
    // statements to handle TypeError exceptions 
} catch (e if e instanceof RangeError) { 
    // statements to handle RangeError exceptions 
} catch (e if e instanceof EvalError) { 
    // statements to handle EvalError exceptions 
} catch (e) { 
    // statements to handle any unspecified exceptions 
    logMyErrors(e); // pass exception object to error handler 
} 

你可以在这里阅读更多：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/try...catch

Answer 3

尝试捕获并没有为我工作。我个人最终测试了响应==“”和状态== 0.

 var req = new XMLHttpRequest(); 
     req.open("post", VALIDATE_URL, true); 
     req.onreadystatechange = function receiveResponse() { 

      if (this.readyState == 4) { 
       if (this.status == 200) { 
        console.log("We go a response : " + this.response); 
       } else if (!isValid(this.response) && this.status == 0) { 
        console.log("The computer appears to be offline."); 
       } 
      } 
     }; 
     req.send(payload); 
     req = null;