我的问题不是关于如何解决 Access-Control-Allow-Origin 问题。执行请求时有时会发生此错误,有时 url 可能已过时。但是我想根据不同的错误为用户打印不同的消息。
目前我有以下代码:
$.ajax(
{
url: link,
type:'HEAD',
timeout: 2000,
error: function(request, status, message)
{
console.log('ajax error');
console.log(request);
console.log(status);
console.log(message);
openPopUp("There was an error accessing the image. It can be because the address is invalid, "+
"or because the server where the image is stored is not allowing direct access to the images.");
},
success: function()
{
// More stuff here
}
});
查看控制台很容易看出文件是否确实丢失,或者是否是访问控制问题。但我想向用户打印出两条不同的消息,准确说明问题所在。查看报错的变量:function(request, status, message) 它们没有变化,这两种情况都会导致404错误。是否有其他人可以这样做,以便我可以知道问题出在哪里?
预先感谢您的关注。
最佳答案
你的浏览器控制台显示你
XMLHttpRequest cannot load http://www.google.com/. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://mysite.com' is therefore not allowed access.
但是您不能单独使用 JavaScript 访问这些信息。当浏览器检测到 CORS 违规时,它将 discard the header information作为协议(protocol)问题。
一种可行的解决方案是使用服务器端代码检查响应 header 并将结果传回您的客户端页面。例如,如果 ajax 请求失败,您可以调用此脚本(我们称之为 cors.php
)并确定它是否包含“Access-Control-Allow-Origin”。
例子:
cors.php?url=http://ip.jsontest.com
cors.php?url=http://www.google.com
返回
Access-Control-Allow-Origin: *
None
因此,您可以在 JavaScript 代码中执行以下操作:
$.ajax({
url: "http://www.google.com",
timeout: 4000,
statusCode: {
404: function() {
// Simple not found page, but not CORS violation
console.log(this.url + " not found" );
}
}
})
.fail(function(jqXHR, textStatus) {
// Empty status is a sign that this may be a CORS violation
// but also check if the request timed out, or that the domain exists
if(jqXHR.status > 0 || jqXHR.statusText == "timeout") {
console.log("Failure because: "+jqXHR.status+" "+jqXHR.statusText+" error");
return;
}
// Determine if this was a CORS violation or not
console.log("Checking if this is a CORS violation at - " + this.url);
$.ajax({
url: "http://myserver.net/cors.php?url=" + escape(this.url),
})
.done(function(msg) {
// Check for the Access-Control-Allow-Origin header
if(msg.indexOf("Access-Control-Allow-Origin") >= 0) {
console.log("Failed bacause '" + msg + "'");
} else {
console.log("Failed bacause of CORS violation");
}
});
})
.done(function(msg) {
// Successful ajax request
console.log(msg);
}); /* Drakes, 2015 */
根据您自己的需要自定义此 PHP 脚本:
<?php
/* cors.php */
$url = $_GET["url"];
if(isset($url)) {
$headers = getHeaders($url, "Access-Control-Allow-Origin");
header("Access-Control-Allow-Origin: *"); // Allow your own cross-site requests
echo count($headers) > 0 ? $headers[0] : "None";
}
// Get the response headers, only specific ones
function getHeaders($url, $needle = false) {
$headers = array();
$ch = curl_init();
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_VERBOSE, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'HEAD'); // Only get the headers
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_NOBODY, true);
curl_setopt($ch, CURLOPT_HEADERFUNCTION, function($curl, $header_line) use(&$headers, $needle) {
if(!$needle || strpos($header_line, $needle) !== false) {
array_push($headers, $header_line);
}
return strlen($header_line);
});
curl_setopt($ch, CURLOPT_URL, $url);
curl_exec($ch);
return $headers;
} /* Drakes, 2015 */
关于javascript - 如何检测ajax错误是Access-Control-Allow-Origin还是文件确实丢失,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22949870/