//html：
<el-form-item label="開始日期" prop="cxBeginTime">
        <el-date-picker
          v-model="queryParams.cxBeginTime"
          type="date"
          placeholder="選擇開始日期">
        </el-date-picker value-format="yyyy-MM-dd" format="yyyy-MM-dd">
</el-form-item>

//data:
queryParams:{cxBeginTime:'',cxEndTime:''},

//
computed: {
      timeDefault() {
        var date = new Date();
        var s1 = date.getFullYear() + "-" + (date.getMonth() + 1) + "-" + (date.getDate()+1);
        return s1;
      }
    },
  mounted() {
        // 初始化查詢，預設為後一天
        this.$set(this.queryParams,"cxBeginTime",this.timeDefault)
        this.$set(this.queryParams,"cxEndTime",this.timeDefault)
 

  },

mounted()裡面，不要用 this.ruleForm.dateValue = this.timeDefault; 這種方式賦值，本文參考 【https://blog.csdn.net/XZZ2222/article/details/91806591?utm_medium=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-BlogCommendFromMachineLearnPai2-1.channel_param