Component navigation guard: write a navigation guard hook function in the js of a certain component
Scope of action : only the current component
to : address to
form : where to come from
(1)beforRouteEhter: Before the component specified by the routing rule is accessed ,
write next(); execute the current page
(2)beforeRouteLeave: automatically trigger when the routing rule leaves the next parameter cannot be written
(3)beforeRouteUpdate: dynamic routing only the parameters change is Only executed (for popular understanding and when jumping to the page)
