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VUE3中watch監(jiān)聽使用實(shí)例詳解

更新時(shí)間：2022年06月07日 11:07:09 作者：莫循瑾木

watch函數(shù)用來偵聽特定的數(shù)據(jù)源,并在回調(diào)函數(shù)中執(zhí)行副作用,下面這篇文章主要給大家介紹了關(guān)于VUE3中watch監(jiān)聽使用的相關(guān)資料,需要的朋友可以參考下

watch介紹

vue中watch用來監(jiān)聽數(shù)據(jù)的響應(yīng)式變化.獲取數(shù)據(jù)變化前后的值

watch的完整入?yún)?/p>

watch(監(jiān)聽的數(shù)據(jù)，副作用函數(shù)，配置對(duì)象)
watch(data, (newData, oldData) => {}, {immediate: true, deep: true})

watch監(jiān)聽的不同情況

創(chuàng)建響應(yīng)式數(shù)據(jù)

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

1 監(jiān)聽單個(gè)refimpl數(shù)據(jù)

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

2 監(jiān)聽多個(gè)refimpl數(shù)據(jù)

方式一：vue3允許多個(gè)watch監(jiān)聽器存在

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

方式二：將需要監(jiān)聽的數(shù)據(jù)添加到數(shù)組

watch([name, age], (newValue, oldValue) => {
  // 返回的數(shù)據(jù)是數(shù)組
  console.log("new", newValue, "old", oldValue);
});

3 監(jiān)聽proxy數(shù)據(jù)

注意

1.此時(shí)vue3將強(qiáng)制開啟deep深度監(jiān)聽

2.當(dāng)監(jiān)聽值為proxy對(duì)象時(shí)，oldValue值將出現(xiàn)異常，此時(shí)與newValue相同

// 監(jiān)聽proxy對(duì)象
watch(person, (newValue, oldValue) => {
  console.log("newValue", newValue, "oldValue", oldValue);
});

4 監(jiān)聽proxy數(shù)據(jù)的某個(gè)屬性

需要將監(jiān)聽值寫成函數(shù)返回形式,vue3無法直接監(jiān)聽對(duì)象的某個(gè)屬性變化

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

注意

當(dāng)監(jiān)聽proxy對(duì)象的屬性為復(fù)雜數(shù)據(jù)類型時(shí)，需要開啟deep深度監(jiān)聽

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

5 監(jiān)聽proxy數(shù)據(jù)的某些屬性

watch([() => person.age, () => person.name], (newValue, oldValue) => {
  // 此時(shí)newValue為數(shù)組
  console.log("person.age", newValue, oldValue);
});