Vue3 watch() 监听

watch()​

侦听一个或多个响应式数据源，并在数据源变化时调用所给的回调函数

 

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<template>     <span>         <p>{{num}}</p>         <p>{{num2}}</p>         <button @click="num++">+1</button>         <button @click="addNum">+1</button>     </span> </template>   <script setup>     import {ref, watch} from "vue"       var num = ref(10)     var num2 = ref(20)       watch(num, (newValue, oldValue) => {         console.log(newValue, oldValue)     })       var addNum = () => {         num.value++;         num2.value++;     }       watch([num, num2], ([newValue, newValue2], [oldValue, oldValue2]) => {         console.log(newValue, oldValue)         console.log(newValue2, oldValue2)     })   </script>