VUE3中watch监听使用实例详解

watch(监听的数据，副作用函数，配置对象)
watch(data, (newData, oldData) => {}, {immediate: true, deep: true})

import { ref, watch, reactive } from "vue";
let name = ref("moxun");
let age = ref(18);
let person = reactive({
  Hobby: "photo",
  city: {
    jiangsu: {
      nanjing: "雨花台",
    },
  },
});

watch(name, (newName, oldName) => {
  console.log("newName", newName);
});

watch(name, (newValue, oldValue) => {
  console.log("new", newValue, "old", oldValue);
});
watch(age, (newValue, oldValue) => {
  console.log("new", newValue, "old", oldValue);
});

watch([name, age], (newValue, oldValue) => {
  // 返回的数据是数组
  console.log("new", newValue, "old", oldValue);
});

// 监听proxy对象
watch(person, (newValue, oldValue) => {
  console.log("newValue", newValue, "oldValue", oldValue);
});

watch(
  () => person.Hobby,
  (newValue, oldValue) => {
    console.log("newValue",newValue, "oldvalue", oldValue);
  }
);

watch(
  () => person.city,
  (newvalue, oldvalue) => {
    console.log("person.city newvalue", newvalue, "oldvalue", oldvalue);
  },{
    deep: true
  }
);

watch([() => person.age, () => person.name], (newValue, oldValue) => {
  // 此时newValue为数组
  console.log("person.age", newValue, oldValue);
});