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
<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>