iview-cli 在webpack.dev.config.js 里的devServer配置代理跨域不生效

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```
devServer:{
historyApiFallback: true,
hot: true,
inline: true,
proxy:{
'/api': {
target: 'http://example.com:8080',
secure: false,
changeOrigin: true,
pathRewrite:{
'^/api':'/api'
}
}
}
}
```

如此配置之后依然无法转发和跨域，参考了goole到的几篇文章，似乎都是这样配的。
参考地址1：https://segmentfault.com/q/1010000011222653
参考地址2：https://hk.saowen.com/a/1bfaaf0ee2020d8736982c9214aeffb83e1fac39b84eacac46388775de49cb38

Start with webpack.dev.config.js and inspect the shown devServer.proxy configuration, then compare it with the referenced proxy guidance. Reproduce a request under /api and determine why it is not forwarded to http://example.com:8080. Done means the configured API request is proxied successfully without the reported cross-origin failure.

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