express使用cros开启跨域访问

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.

  
 

  
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项目结构

├── index.html
├── index.js
└── package.json

  
 

  
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package.json

{
  "dependencies": { "cors": "^2.8.5", "express": "^4.17.1"
  }
}
  
 

  
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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/')
})

  
 

  
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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>

  
 

  
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通过以上代码就可以正常请求获取后台数据了

文章来源: pengshiyu.blog.csdn.net，作者：彭世瑜，版权归原作者所有，如需转载，请联系作者。

原文链接：pengshiyu.blog.csdn.net/article/details/105718270