从新回归Vue之3.0（三）Watch,WatchEffect，生命周期

一，Watch和WatchEffect使用方法

类似于之前的Watch监听，推荐watch监听

1、watch和watchEffect都懒执行副作用，不过watchEffect比较频繁，在vue组件更新之前执行；
2、watch更具体地说明什么状态应该触发侦听器重新运行，watchEffect就没有这么友好；
3、watch访问侦听状态变化前后的值。

<template>
  <p>{{ count }}</p>
  <p>{{ originData.count }} {{ originData.user.name }}</p>
  <button @click="incriment">点击我count增加</button>
</template>
 
<script setup lang="ts">
import { ref, reactive, watchEffect, watch } from "vue";
// data
const count = ref(0);
const user = reactive({ name: "张三" });
const arr = reactive([1, 2, 3, 4]);
const originData = reactive({
  count: 0,
  user: {
    name: "张三",
  },
  arr: [1, 2, 3, 4],
});
// props
// emit
// methods
const incriment = () => {
  console.log(originData.user);
  originData.count++;
  count.value++;
  originData.user.name = "李四";
};
//watch
watch(
  [count, originData.user],
  (newVals, oldVals) => {
    console.log("newVals", newVals);
    console.log("oldVals", oldVals);
  },
  {
    deep: true,
    immediate: true,
  }
);
// defineExpose
</script>

二，在setup中的生命周期钩子

因为 setup 是围绕 beforeCreate 和 created 生命周期钩子运行的，所以不需要显式地定义它们。换句话说，在这些钩子中编写的任何代码都应该直接在 setup 函数中编写。

选项式 API      Hook inside setup
beforeCreate   Not needed* 不需要
created            Not needed* 不需要
beforeMount    onBeforeMount 挂载之前
mounted          onMounted 页面加载完成时执行
beforeUpdate  onBeforeUpdate
updated           onUpdated
beforeUnmount   onBeforeUnmount
unmounted   onUnmounted 页面销毁时执行
errorCaptured   onErrorCaptured
renderTracked   onRenderTracked
renderTriggered   onRenderTriggered
activated   onActivated
deactivated   onDeactivated

import { onMounted, onActivated, onUnmounted, onUpdated, onDeactivated } from "vue";
// 生命周期
onMounted(() => {
  console.log("组件挂载");
});
 
onUnmounted(() => {
  console.log("组件卸载");
});
 
onUpdated(() => {
  console.log("组件更新");
});
onActivated(() => {
  console.log("keepAlive 组件 激活");
});
 
onDeactivated(() => {
  console.log("keepAlive 组件 非激活");
});