vue2

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
<template>
  <h2>{{ message }}</h2>
  <button @click="info.name = 'kkk'">修改message</button>
  <button @click="info.friends.name = 'oooo'">修改message</button>
</template>

<script>
export default {
  data() {
    return {
      info: {
        name: "ddd",
        friends: { name: "ppp" },
      },
    };
  },
  watch: {
    info: {
      handler: (newValue, oldvalue) => {
        console.log(newValue, oldvalue);
      },
      immediate: true,
      deep: true,
    },
  },
};
</script>

vue3

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
<template>
  <h2>{{ message }}</h2>
  <button @click="message = 'ooo'">修改message</button>
  <button @click="info.name = 'ooo'">修改message</button>
  <button @click="info.friends.name = 'james'">修改message</button>
</template>

<script setup>
import { ref, watch, reactive } from "vue";
const message = ref("hello");
const info = reactive({
  name: "hh",
  friends: { name: "jack" },
});
watch(message, (newValue, oldValue) => {
  console.log(newValue, oldValue);
});


/**
 * 响应式对象 默认进行了深度监听
 * 并且newValue oldValue指向同一内存地址
 * 所以newValue里的info.name改变了，打印出来的oldValue里的info.name也会改变
 */
//Proxy {name: 'ooo', friends: {…}}[[Handler]]: Object[[Target]]: Object[[IsRevoked]]: false Proxy {name: 'ooo', friends: {…}}
watch(info, (newValue, oldValue) => {
  console.log(newValue, oldValue);
});



/**
 * 这种情况的info不是响应式对象，深度监听要配置deep
 * 且返回的不再是proxy代理对象
 */
watch(
  () => ({ ...info }),
  (newValue, oldValue) => {
    console.log(newValue, oldValue);
  },
  { deep: true, immediate: true }
);
</script>

watchEffect

watchEffect 会自动收集依赖，依赖改变，就会执行函数

1
2
3
4
5
const counter = ref(0);
watchEffect(() => {
  console.log(counter.value);
});
</script>

停止监听

1
2
3
4
5
6
7
8
const counter = ref(0);
const stopWatch = watchEffect(() => {
  console.log(counter.value);

  if (counter.value > 5) {
    stopWatch();
  }
});