服务器端设置可以跨域

// 设置允许跨域访问该服务
app.all('*', function (req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header('Access-Control-Allow-Methods', 'PUT, GET, POST, DELETE, OPTIONS');
  res.header("Access-Control-Allow-Headers", "X-Requested-With, Content-Type, mytoken");
  next();
});