一、props解构，默认值

vue3

const { count = 0, message = 'hello' } = withDefaults(   defineProps<{     count?: number     message?: string   }>(),   {     count: 0,     message: 'hello'   } )

vue3.5 

const { count = 0,message = 'hello'} =  defineProps<{   count?: number;   message?: string; }>()

二、useId

全局唯一id-----一个app内 

const id = useId()

三、useTemplateRef

通过ref获取dom

vue3

const button = ref(null)

vue3.5 

const el = useTemplateRef('button') console.log(el, 'dom')

四、watch新增 onCleanup回调

vue3.5

onCleanup---下一次watch执行前触发---可以在这里移除上一次watch

watch(count, (newVal, oldVal, onCleanup) => {   const handler = () => {     console.log(newVal, 'newVal')   }   addEventListener('click', handler)   onCleanup(() => {     removeEventListener('click', handler)   }) })

完整代码