first of all, your route should be wrapped with < kepp-alive > , so that the routing component will not be destroyed when switching. It is easy to understand this and solve the problem.

confirm what is listening in the watch option on the A page, and then check whether the B page has changed the content.

if you want to keep < keep-alive > and do not want A component watch to be executed on other pages, you can make a judgment on the routing attribute $route in the function:

    watch: {
        something(newValue, oldValue) {
            if (this.$route.fullPath === 'A') {
                // do something
            }
        }
    }

watch belongs to vue api has nothing to do with vue-router. For more information, please see https://cn.vuejs.org/v2/api/-sharp.
listens for route changes, the route has two actions, to,from. That's why you triggered it twice. Watch is written on page a, and other page switches will not be triggered, of course. no, no, no.

is keep-alive? used?