https://www.cnblogs.com/pass245939319/p/9040802.html
使用cors：
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");
if (req.method === 'OPTIONS') {
res.send(200)
} else {
next()
}
});
