介面呼叫：

this.$ajax.get('http://localhost:3000/users').then((res)=>{
      console.log(res,222222222222)
    })

然而這個時候，頁面報錯了，錯誤如下

解決方法是

app.all('*', function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "X-Requested-With,Content-Type");
  res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");
  next();
});