【发布时间】：2014-03-25 11:04:41
【问题描述】：
大家好，我正在尝试通过以下方式关闭缓存 向随请求消息一起发送的 URL 的查询字符串组件添加随机值。
我有一个服务器将 etag 作为字符串发送给我的客户端，我想确保没有缓存正在进行我已经 setRequestHeaders 但我还应该添加一个类似于 POST /message?x= 的 http 请求0.123456789 HTTP/1.1
这是我的客户代码
<html>
<header><title>This is title</title></header>
<body>
<span id="ajaxButton" style="cursor: pointer; text-decoration: underline">
Make a request
</span>
<script type="text/javascript">
(function() {
var httpRequest;
var x= Math.random();
document.getElementById("ajaxButton").onclick = function() { makeRequest('http://localhost:5000/'); };
function makeRequest(url) {
if (window.XMLHttpRequest) { // Mozilla, Safari, ...
httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) { // IE
try {
httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e) {
try {
httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e) {}
}
}
if (!httpRequest) {
alert('Giving up :( Cannot create an XMLHTTP instance');
return false;
}
httpRequest.onreadystatechange = alertContents;
httpRequest.open('GET', url, true);
//httpRequest.setRequestHeader("pragma", "no-cache");
//httpRequest.setRequestHeader("Cache-Control", "no-cache", "no-store");
httpRequest.send();
}
function alertContents() {
if (httpRequest.readyState === 4) {
if (httpRequest.status === 200) {
var etagString = httpRequest.responseText;
alert(etagString);
} else {
alert('There was a problem with the request.');
}
}
}
})();
</script>
</body>
</html>
编辑添加错误
XMLHttpRequest cannot load http://localhost:5000/?_0.1909303846769035. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.
使用 node.js 我使用 main.js 运行服务器
var http = require('http');
var domain = require('domain');
var root = require('./root'); // do I have to replace root w/ message
var image = require('./image'); // for better readability?
function replyError(res) {
try {
res.writeHead(500);
res.end('Server error.');
} catch (err) {
console.error('Error sending response with code 500.');
}
};
function replyNotFound(res) {
res.writeHead(404);
res.end('not found');
}
function handleRequest(req, res) {
console.log('Handling request for ' + req.url);
if (req.url === '/') {
root.handle(req, res);
}
if (req.url === '/image.png'){
image.handle(req, res);
}
else {
replyNotFound(res);
}
}
var server = http.createServer();
server.on('request', function(req, res) {
var d = domain.create();
d.on('error', function(err) {
console.error(req.url, err.message);
replyError(res);
});
d.run(function() { handleRequest(req, res)});
});
function listen(){
server.listen(5000);
}
root.init(listen);
在root.js里面是
var http = require('http');
var response = require('./response');
var body;
var etag;
exports.handle = function(req, res) {
if (req.headers['if-none-match'] === etag) {
console.log('returning 304');
return response.replyNotModified(res);
}
res.writeHead(200, {'Content-Type': 'text/plain',
'Content-Length': body.length,
"Access-Control-Allow-Origin":"*",
"Access-Control-Allow-Headers":"X-Requested-With",
'ETag' : etag
});
res.end(body);
}
exports.init = function(cb) {
require('fs').readFile('app.html', function(err, data) {
if (err) throw err;
etag = response.generateETag(data); //
body = etag;
console.log("init");
cb();
});
}
/*function generateETag(buffer) {
var shasum = require('crypto').createHash('sha1');
shasum.update(buffer, 'binary');
return shasum.digest('hex');
console.log(shasum.digest('hex'));
}
var replyNotModified = function(res) {
res.writeHead(304);
res.end();
};*/
错误在
【问题讨论】：
-
那么你的问题是什么？
-
如何使用 math.random() 添加随机值
-
您说它会抛出错误，但您没有向我们提供这些错误。如果您给我们一些日志输出或控制台输出，以便我们可以在您使用 math.random() 函数时看到它们是什么，这将有所帮助。
-
您使用什么 url 来访问发出此请求的页面？对我来说似乎是一个跨域问题。
-
我添加了错误我应该添加我的服务器端js代码吗？
标签： javascript node.js caching