监听对象中某个属性值的变化

      <el-form ref="form" :key="formKey" :model="formData" class="cncform" :rules="rules" label-width="140px">
       
 <el-form-item label="供应商和制造片区" prop="supplier">
              <el-select v-model="formData.supplier" placeholder="请选择供应商" style="width: 100%" @change="supplierChange">
                <el-option v-for="item in supplierOptions" :key="item.value" :label="item.label" :value="item.value" />
              </el-select>
            </el-form-item>
</el-form>

<script>
export default { 
      data() {
    return {
        formData:{
            supplier:""
        }
    },
     watch: {
               'formData.supplier': {
      handler(newVal) {
//再这里就可以监听到
            console.log(newVal,'newVal')
      },
      deep: true
    },     



    }
  },  
    
}

</script>