javascript 获取响应中缺少标头
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Missing headers in Fetch response
提问by william
I need to make a CORS post request. I need to use fetchbecause axios's responseis already processed to json.
我需要制作一个CORS post request. 我需要使用，fetch因为axios'sresponse已经处理为 json。
But in fetchresponse, the headersis empty. But I don't think this is the server problem since axiosresponse headers have the values that I want.
但作为fetch回应，headers是空的。但我不认为这是服务器问题，因为axios响应标头具有我想要的值。
Any trick?
有什么技巧吗？
fetch('http://localhost:9876/test/sample-download', {
method: 'post',
headers: {},
body: {}
})
.then(response => {
console.log(response);
})
.catch(err => console.error(err));
axios.post('http://localhost:9876/test/sample-download', {}, {})
.then(response => console.log(response))
.catch(error => console.error(error));
回答by ccnokes
The Headersclass instance that fetch returns is an iterable, as opposed to a plain object like axios returns. Some iterable's data, such as Headers or URLSearchParams, aren't viewable from the console, you have to iterate it and console.log each element, like:
fetch 返回的Headers类实例是一个可迭代的，而不是像 axios 返回的普通对象。某些可迭代的数据，例如 Headers 或 URLSearchParams，无法从控制台查看，您必须迭代它和 console.log 每个元素，例如：
fetch('http://localhost:9876/test/sample-download', {
method: 'post',
headers: {},
body: {}
})
.then(response => {
// Inspect the headers in the response
response.headers.forEach(console.log);
// OR you can do this
for(let entry of response.headers.entries()) {
console.log(entry);
}
})
.catch(err => console.error(err));
回答by AndyTheEntity
Headers are limited for CORS requests. See https://stackoverflow.com/a/44816592/2047472
标头仅限于 CORS 请求。见https://stackoverflow.com/a/44816592/2047472
(Use access-control-expose-headersto allow exposing headers to requests from a different origin.)
（access-control-expose-headers用于允许向来自不同来源的请求公开标头。）
回答by Vijay kumar Pendem
To get a specific header property you can use the following:
要获取特定的标题属性，您可以使用以下内容：
response.headers.get(yourProperty)
回答by Carlos Verdes
Although the correct answer is the one from @AndyTheEntity for me is a little bit incomplete.
虽然正确答案是@AndyTheEntity 对我来说有点不完整。
CORS requests have limitations and show only a subset of headers:
CORS 请求有限制，仅显示标头的子集：
Cache-ControlContent-LanguageContent-TypeExpiresLast-ModifiedPragma
Cache-ControlContent-LanguageContent-TypeExpiresLast-ModifiedPragma
In order to show more headers on the response, the serverhas to add a header to allow more extra headers.
为了在响应中显示更多标头，服务器必须添加一个标头以允许更多额外标头。
For example, after a POST request if a new resource is created you should return a 201 CREATED response and add a Locationheader.
If you need to accept CORS also you need to add the next headers (on the serverresponse):
例如，在创建新资源的 POST 请求之后，您应该返回 201 CREATED 响应并添加Location标头。如果您还需要接受 CORS，您还需要添加下一个标头（在服务器响应中）：
Location: $url-of-created-resource
Access-Control-Expose-Headers: Location
With this you will see on the client the header Location.
有了这个，您将在客户端上看到标题Location。
If you need to send an specific header (like a SESSION_ID), then you need to add the next header in the request:
如果您需要发送特定标头（如 a SESSION_ID），则需要在请求中添加下一个标头：
Access-Control-Request-Headers: SESSION_ID
SESSION_ID: $current_session_id
I hope this cover all needs to handle request/response using CORS.
我希望这涵盖了使用 CORS 处理请求/响应的所有需求。
