beforeRouteEnter

The beforeRouteEnter guard is a navigation guard in Vue Router. It is invoked before a route is entered. This guard is primarily used for fetching data that is required for the component before it is rendered. Unlike other route guards, beforeRouteEnter has access to the `next` callback which must be called to resolve the navigation. The `next` callback can either be called with a boolean to indicate whether to proceed with the navigation, or with a new route object to redirect.

The most distinctive feature of beforeRouteEnter is that the component instance is not yet created when this guard is called. Therefore, you cannot access `this` inside the guard. Instead, you can access the component instance via the `vm` argument passed to the next callback. This allows you to perform actions on the component instance, such as setting data properties, after the component has been instantiated but before it is mounted.

The signature of beforeRouteEnter is: `(to, from, next) => { ... }`. The `to` and `from` arguments are Route objects representing the target and current routes, respectively. The `next` function is crucial for controlling navigation. If `next()` is called without arguments, navigation proceeds. If `next(false)` is called, navigation is cancelled. If `next('/path')` or `next({ path: '/path' })` is called, navigation is redirected to the specified path.