keep-alive component is an abstract Vue provide to cache components, thereby saving performance,
Because it is an abstract component, so after v page rendering is completed will not be rendered into a DOM element
When the switch assembly is activated in the keep-alive component, deactivated two lives
Cycle hook function is executed
example:
h3 label binding event, when clicking the color red
<Keep-alive> saved to the cache tag parcel routing
Route Object:
When switching routed back, then any previously saved state
