一：通过watch来监听数据变化，并通过打印显示

<template>
  <div  class="personal-center">
    <input type="text" placeholder="请输入" v-model="inputVal"/>
    <p>{{newVal}}</p>
  </div>
</template>
<script>
  export default {
    name: 'demo',
    data() {
      return {
        inputVal: '',
        newVal:''
      }
    },
    watch: {
      inputVal(newVal, oldVal) {
        this.newVal = newVal
        console.log("inputVal = " + newVal + " , oldValue = " + oldVal)
      }
    }
  }
</script>

效果图：

二：首次渲染开启监听
按上面的代码实现，网页首次渲染是不会启动监听的，如果我们需要第一次渲染变开启监听，这时只需要设置immediate： true,

watch: {
      inputVal(newVal, oldVal) {
        this.newVal = newVal
        console.log("inputVal = " + newVal + " , oldValue = " + oldVal)
      },
      immediate: true,
    }

三：深度监听
当我们监听的数据是对象或数组时，需要开启深度监听才行。这时也仅仅需要加一行代码：deep: true

watch: {
      inputVal(newVal, oldVal) {
        this.newVal = newVal
        console.log("inputVal = " + newVal + " , oldValue = " + oldVal)
      },
      immediate: true,
      deep: true
    }