javascript - 全局变量在开关内不起作用 - javascript

Question

 let visitor;
 const role = req.user.profile;

 // role will be either Admin or Manager

 switch (role) {
   case 'Admin':
     if (req.body.verificationMode === 'online') {
       visitor = {
         name: req.body.name,
         mode: 'online',
       };
     } else {
       visitor = {
         name: req.body.name,
         mode: 'offline'
       };
     }
     break;


   case 'Manager':
     Staff.findOne({
       where: {
         loginId: req.user.id,
       },
     }).then((staffData) => {
       if (req.body.verificationMode === 'online') {
         visitor = {
           name: req.body.name,
           mode: 'online',
         };
       } else {
         visitor = {
           name: req.body.name,
           mode: 'offline',
         };
       }
     });
     break;

 }
 console.log('visitor >>> >> >> >> >>> >>>> >>>> >>>> >>> >>>> >>>', visitor);

如果我以管理员 Angular 色登录，访问者控制台具有正确的数据，但如果以经理 Angular 色登录，访问者控制台将变为未定义 .

为什么会发生这种情况？我使用的是 ES6，所以我不使用 var。

Answer 1

如果 Manager 在 console.log 之后执行，则您有异步代码。这就是为什么在这种情况下访问者是未定义的。

用这个。

 let visitor;
 const role = req.user.profile;
 let callback = function(){
     console.log('visitor >>> >> >> >> >>> >>>> >>>> >>>> >>> >>>> >>>', visitor); 
 }
 // role will be either Admin or Manager



 switch (role) {
   case 'Admin':
     if (req.body.verificationMode === 'online') {
       visitor = {
         name: req.body.name,
         mode: 'online',
       };
     } else {
       visitor = {
         name: req.body.name,
         mode: 'offline'
       };
     }
     callback();
     break;


   case 'Manager':
     Staff.findOne({
       where: {
         loginId: req.user.id,
       },
     }).then((staffData) => {
       if (req.body.verificationMode === 'online') {
         visitor = {
           name: req.body.name,
           mode: 'online',
         };
       } else {
         visitor = {
           name: req.body.name,
           mode: 'offline',
         };
       }
       callback();
     });
     break;

 }

将 console.log 移动到一个函数中，该函数在 visitor 值初始化后调用。