javascript 在 node.js 中，如何获取响应 http.get() 的 Content-Length 标头？
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In node.js, how do I get the Content-Length header in response to http.get()?
提问by mike
I have the following script and it seems as though node is not including the Content-Length header in the response object. I need to know the length before consuming the data and since the data could be quite large, I'd rather not buffer it.
我有以下脚本，似乎 node 没有在响应对象中包含 Content-Length 标头。我需要在使用数据之前知道长度，并且由于数据可能非常大，我宁愿不缓冲它。
http.get('http://www.google.com', function(res){
console.log(res.headers['content-length']); // DOESN'T EXIST
});
I've navigated all over the object tree and don't see anything. All other headers are in the 'headers' field.
我已经浏览了整个对象树，但什么也没看到。所有其他标题都在“标题”字段中。
Any ideas?
有任何想法吗？
采纳答案by josh3736
www.google.com does not send a Content-Length. It uses chunked encoding, which you can tell by the Transfer-Encoding: chunkedheader.
www.google.com 不会发送Content-Length. 它使用分块编码，您可以通过Transfer-Encoding: chunked标头来判断。
If you want the size of the response body, listen to res's dataevents, and add the size of the received buffer to a counter variable. When endfires, you have the final size.
如果您想要响应正文的大小，请侦听res的data事件，并将接收到的缓冲区的大小添加到计数器变量中。当end火灾，你有最后的大小。
If you're worried about large responses, abort the request once your counter goes above how ever many bytes.
如果您担心大的响应，一旦您的计数器超过多少字节就中止请求。
回答by Chad
Not every server will send content-lengthheaders.
并非每个服务器都会发送content-length标头。
For example:
例如：
http.get('http://www.google.com', function(res) {
console.log(res.headers['content-length']); // undefined
});
But if you request SO:
但是，如果您要求 SO：
http.get('http://stackoverflow.com/', function(res) {
console.log(res.headers['content-length']); // 1192916
});
You are correctly pulling that header from the response, google just doesn't send it on their homepage (they use chunked encoding instead).
您正确地从响应中提取该标头，谷歌只是没有在他们的主页上发送它（他们使用分块编码）。
