如果跨域，前端直接请求后端数据会报错
Access to XMLHttpRequest at 'http://127.0.0.1:8080/' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
项目结构
├── index.html
├── index.js└── package.json
package.json
{
"dependencies": {
"cors": "^2.8.5",
"express": "^4.17.1"
}
}
index.js
var express = require('express')
var cors = require('cors')
var app = express()
app.use(cors())
app.get('/', function (req, res) {
res.send("hello")
})
app.listen(8080, function () {
console.log('listening: http://127.0.0.1:8080/')
})
index.html
<script>
var request = new XMLHttpRequest();
request.open('GET', 'http://127.0.0.1:8080', true)
request.send(null)
request.onreadystatechange = function () {
if (request.readyState == 4 && request.status == 200) {
console.log(request.responseText);
}
}
</script>
通过以上代码就可以正常请求获取后台数据了
</div>