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[英]Error “No 'Access-Control-Allow-Origin' header is present on the requested resource” even after setting headers on server and client
[英]Why there is still a cross oorigin error after setting the Access-Control-Allow-Origin in server side?
我刚刚运行了一个 CORS 跨域演示。演示与 node.js 一起运行。 这里是索引。html:
<button>click to cross origin using CROS</button>
<p>hello world 😘</p>
<script>
var btn = document.getElementsByTagName('button')[0];
var text = document.getElementsByTagName('p')[0];
btn.addEventListener('click', function () {
var xhr = new XMLHttpRequest();
var url = 'http://localhost:3001';
xhr.open('PUT',url,true);
xhr.send();
xhr.onreadystatechange = () => {
if (xhr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
text.innerHTML = xhr.response;
}
}
})
</script>
这是 serverRes.js:
var express = require('express');
var app = express();
var responsePort = 3001;
app.get('/', (req, res) => {
res.set('Access-Control-Allow-Origin', 'http://localhost:3000');
res.send("Hello world from CROS.😡");
});
app.listen(responsePort, function () {
console.log('cros_responser is listening on port '+ responsePort);
});
你可以看到我已经用http://localhost:3000
设置了Access-Control-Allow-Origin
,所以对预检请求的响应实际上应该通过访问控制检查,这意味着请求无论如何都会成功。但是当我go 到端口 3000,我得到的是:
但是为什么呢?为什么在服务器端设置了Access-Control-Allow-Origin后还是会出现cross origin错误? 另外,我试过写:
app.all('/', function (req, res, next) {
res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
res.send("Hello world from CROS.😡");
next(); // pass control to the next handler
});
根据为什么不将 CORS 标头添加到 OPTIONS 路由允许浏览器访问我的 API? . 但是错误仍然存在。
您发布的代码应该可以工作。
var express = require('express');
var app = express();
var responsePort = 3001;
app.all("/", function(req, res, next){
res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
next();
});
app.get('/', (req, res) => {
res.set('Access-Control-Allow-Origin', 'http://localhost:3000');
res.send("Hello world from CROS.😡");
});
app.listen(responsePort, function () {
console.log('cros_responser is listening on port '+ responsePort);
});
尝试点击这个 repl。
您还需要使用 header Access-Control-Allow-Methods
http 动词:
res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
这个答案有更详细的描述: Why does not adding CORS headers to an OPTIONS route allow browsers to access my API?
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