xmlHttpRequest.onerror处理程序用例 [英] xmlHttpRequest.onerror handler use case

问题描述

哪种情况会导致调用此处理程序？我找不到这个方法抛出错误的任何实例。

我试着让设备离线，我得到 xmlHttpRequest.status = 0 但没有错误。

问题是我可以创建哪种情况来测试此处理程序的功能。

  var xmlhttp = new XMLHttpRequest（），
 method ='GET'，
 url ='https：//developer.mozilla。组织/'; 
 
 xmlhttp.open（method，url，true）; 
 xmlhttp.onerror = function（）{
 console.log（**交易期间发生错误）; 
}; 
 xmlhttp.send（）; 
  

来自：

在这里，亲自尝试：

  var xmlhttp = new XMLHttpRequest（），method ='GET'，url ='https://developer.mozilla.org/';xmlhttp.open(method,lll,true）; xmlhttp.onerror = function（）{console.log（ **交易期间发生错误）;}; xmlhttp.send（）;  

在处理任何基于网络的IO时，可能会发生各种各样的事情。跨源请求只有一个。如果服务器处于脱机状态，DNS查找失败，您和服务器之间的关键故障点之间的路由器出现故障怎么办？

What sort of situations could cause this handler to be called? I'm not finding any instance where this method throws an error.

I tried with the device offline, I get xmlHttpRequest.status = 0 but no error.

Question is what sort of situations can I create in order to test functionality of this handler.

var xmlhttp = new XMLHttpRequest(),
  method = 'GET',
  url = 'https://developer.mozilla.org/';

xmlhttp.open(method, url, true);
xmlhttp.onerror = function () {
  console.log("** An error occurred during the transaction");
};
xmlhttp.send();

From: https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequestEventTarget/onerror

解决方案

Your question is the perfect example. Just try your code from your web developer console while on this very page.

Here, try it yourself:

var xmlhttp = new XMLHttpRequest(),
  method = 'GET',
  url = 'https://developer.mozilla.org/';

xmlhttp.open(method, url, true);
xmlhttp.onerror = function () {
  console.log("** An error occurred during the transaction");
};
xmlhttp.send();

When dealing with any network based IO all kinds of things could happen. Cross-Origin requests are only one. What if the server is offline, DNS lookup fails, a router between you and the server that is critical point of failure goes down?

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