export default {
    props: {
        title: String,
    },
    data() {
        return {
            username: "",
            password: "",
        };
    },
    methods: {
        login() {
            //登錄axios請求處理
        },
    },
    components: {
        buttonComponent: btnComponent,
    },
    computed: {
        fullName() {
            return this.firstName + " " + this.lastName;
        },
    },
};

export default {
    props: {
        title: String,
    },
    setup() {
        const state = reactive({
            //數(shù)據(jù)
            username: "",
            password: "",
            lowerCaseUsername: computed(() => state.username.toLowerCase()), //計算屬性
        });
        //方法
        const login = () => {
            //登錄axios請求處理
        };
        return {
            login,
            state,
        };
    },
};

Vue2--------------vue3
beforeCreate  -> setup()
created       -> setup()
beforeMount   -> onBeforeMount
mounted       -> onMounted
beforeUpdate  -> onBeforeUpdate
updated       -> onUpdated
beforeDestroy -> onBeforeUnmount
destroyed     -> onUnmounted
activated     -> onActivated
deactivated   -> onDeactivated

<template>
  <div id="app">
    <nav-View v-show="login" />
    <router-view v-if="isRouterAlive" /> <!-- 進行v-if判斷 -->
    <foot-View v-show="login" />
  </div>
</template>

<script>
import navView from "@/components/navView.vue";
import footView from "@/components/footer.vue";
import { onMounted, ref, watch ,nextTick,provide,} from "vue";//要引入方法
import { useRouter } from "vue-router";

export default {
  name: "app",
  components: {
    navView,
    footView,
  },
  created() {
    console.log("123", this.$route.path);
  },
  setup() {
    // 局部組件刷新
    const isRouterAlive = ref(true);
    const reload = () => {
      isRouterAlive.value = false;
      nextTick(() => {
        isRouterAlive.value = true;
      });
    };
    provide("reload", reload);
    return {
      isRouterAlive,
    };
  },
  watch: {
    
  },
};
</script>

<style>
* {
  margin: 0px;
}
#app {
  font-family: "Avenir", Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
}
</style>

<template>
  <div>
    <!-- input框輸入值，點擊按鈕，看值會不會清空 -->
    <input type="text"> 
  </div>
  <button @click="refresh">頁面刷新</button>
</template>
<script>
import { inject } from "vue";
export default{
  setup() {
    const refresh = inject("reload");
	//在方法體中的調用方法
    // refresh();
    return {
      refresh,
    };
  },
};
</script>