such a scenario:
let g=""
router.get("/",function(req,res,next){
/*g*/
g="date"
}
router.get("/next",function(req,res,next){
/*g*/
} every time the user enters / assigns the global gjinghort next route, it needs to operate according to g. If the null value jumps /, it is not a null value to proceed to the next operation.
if user An enters first, modify the gaming matching data Aids, and then user B goes to modify the gaming matching data Bones. If user A requests / next, at this time, the g value should be dataB, but will actually operate further according to dataA, g is a global common variable, and B enters after A, why do you operate according to dataA?