在开本地服务器与其他人协作开发测试接口时，前端发送请求时遇到Access-Control-Allow-Origin的错误，此时只需要在后台加上

app.use('*', function (req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "Content-Type,Content-Length, Authorization, Accept,X-Requested-With");
    res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");
    res.header("X-Powered-By",' 3.2.1');
    if(req.method=="OPTIONS") res.send(200);/*让options请求快速返回*/
    else  next();
});