1、有哪些生命周期
beforeCreate
created
beforeMount
mounted
beforeUpdate
updated
beforeDestroy
destroyed
第一次进入组件执行哪些生命周期
beforeCreate
created
beforeMount
mounted
如果使用 keep-alive会多出两个生命周期
activated
deactivated
此时第一次进入组件会执行 beforeCreated created beforeMount mounted activated 生命周期 再次进入组件只会执行 activated生命周期
