生命周期

• 去除beforeCreate与created，使用setup()代替
• 新增onRenderTracked、onRenderTriggered。类似wathcEffect中的onTrack与onTrigger

名称	描述
onBeforeMount	替换beforeMount
onMounted	替换mounted
onBeforeUpdate	替换beforeUpdate
onUpdated	替换updated
onBeforeUnmounted	替换beforeDestroy
onUnmounted	替换destroyed
onErrorCaptured	替换errorCatured

import { onMounted, watchEffect } from 'vue'

const count = ref(0);
onMounted(() => {
  watchEffect(() => {
    console.log(count.value) 
  })
})