//server.js设置跨域访问

app.all('*', function(req, res, next) {    res.header("Access-Control-Allow-Origin", req.headers.origin); //需要显示设置来源    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");    res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");    res.header("Access-Control-Allow-Credentials",true); //带cookies    res.header("X-Powered-By",' 3.2.1')    res.header("Content-Type", "application/json;charset=utf-8");    next();});

//web.js

//原生var xhr = new XMLHttpRequest();xhr.open("post", "xxx/xxx", true);xhr.withCredentials = true;//放在 open 方法后面比较靠谱xhr.onload = function(){}xhr.send("a=1&b=2");//ajax$.ajax({        type:'get',        url:"http://localhost:3000/logouts",        dataType:"json",        xhrFields: {              withCredentials: true              },        success:function(data){          console.log(data);        }      })　　

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