the front and back ends are developed separately, and ajax is used to access the background interface. 
 solved this cross-domain problem for the first time, and I don"t know what went wrong. 
 there is really nothing I can do. 
js Code
url:"/v1/user/login",
data:"username=" + loginUserName + "&password="+loginUserPassword,
type:"get",
dataType:"json",
success:function(data){
    location.href = "../index/index.html";
},
failure:function(){
    alert("");
}
webpack.config.js configuration is written like this
    devServer: {
        historyApiFallback: true,
        hot: true,
        inline: true,
        progress: true,
        proxy: {
            "/v1/*": {
                target: "http://192.xxx.xxx.xxx:8080",//
                changeOrigin: true,
                secure: false,
            }
        }
    },
Code display:
 
jsonp
js
 
