vue,element-ui 表單驗(yàn)證出錯(cuò)，value.getTime is not a function

效果如圖

現(xiàn)在問(wèn)題是，每次點(diǎn)擊提交之后，都會(huì)如下報(bào)錯(cuò)：

查了一遍之后，有一種說(shuō)法是el-date-picker本身支持字符串和date object兩種類型，但是json中的字符串綁定之后在效驗(yàn)時(shí)就不是date object，所以出現(xiàn)了異常。所以加上that.newForm.useTime=moment(that.newForm.useTime).toDate();進(jìn)行轉(zhuǎn)換可是還是報(bào)錯(cuò)。
代碼圖片和源碼如下，請(qǐng)大神指教，謝謝！
HTML：

rules:

js:

（忽略params里freeTime:that.newForm.useTime,少了一個(gè)newForm，修改的時(shí)候粗心了）
源碼：
html：

<el-button type="primary" icon="plus" @click="newDialogVisible = true">新增賬號(hào)</el-button>
            <el-dialog title="新增賬號(hào)" v-model="newDialogVisible"  @close="resetForm1('newForm')">
            <el-form :model="newForm"  :rules="rules1" ref="newForm" :label-width="formLabelWidth">
              <el-form-item label="廠家名稱" prop="nickName">
                <el-input v-model="newForm.nickName" auto-complete="off" style="width:70%;"></el-input>
              </el-form-item>
              <el-form-item label="賬號(hào)" prop="userAccount">
                <el-input v-model="newForm.userAccount" @blur="checkName" auto-complete="off" style="width:70%;"></el-input>
              </el-form-item>
              <el-form-item label="密碼" prop="userPasswd">
                <el-input v-model="newForm.userPasswd" auto-complete="off" style="width:70%;"></el-input>
              </el-form-item>
              <el-form-item label="實(shí)體店最大數(shù)量"prop="maxNumber">
                <el-input v-model.number="newForm.maxNumber" auto-complete="off" style="width:70%;"></el-input>
              </el-form-item>
              <el-form-item label="到期時(shí)間" prop="useTime">
                  <el-date-picker
                    v-model="newForm.useTime"
                    style="width:70%;"
                    type="date"
                    placeholder="選擇日期"
                   >
                  </el-date-picker>
              </el-form-item>
              <el-form-item label="備注">
                <el-input v-model="newForm.remark" auto-complete="off" style="width:70%;"></el-input>
              </el-form-item>
            </el-form>
            <div slot="footer" class="dialog-footer">
              <el-button type="primary" @click="addAcount('newForm')">保 存</el-button>
              <el-button @click="resetForm1('newForm')">取 消</el-button>
            </div>
          </el-dialog>

js:

  //添加
    addAcount:function(formName){
     let that = this     
     that.newForm.useTime=moment(that.newForm.useTime).format('YYYY-MM-DD');
     // alert(that.newForm.useTime)
     that.$refs[formName].validate((valid) => {
          if (valid) {
              // that.newForm.useTime=moment(that.newForm.useTime).toDate();
              that.$http.post(config.URL+'platform/user/add',
              {},
              {
              params:{
                 username:that.newForm.userAccount,
                 password:that.newForm.userPasswd,
                 nickname:that.newForm.nickName,
                 freeTime:that.newForm.useTime,
                 maxNumber:that.newForm.maxNumber,
                 remark:that.newForm.remark
               },
               emulateJSON:true
             })
            .then(
            function(res){
              if (res.body.code==1) {
                that.show();
                that.$refs[formName].resetFields();
                that.newDialogVisible = false
              }
              else{
                Message.error(res.body.statusMsg);
              }
            },
            function(err){
                Message.error('與服務(wù)器連接錯(cuò)誤！');             
            }) 
          } else {
            console.log('error submit!!');
            return false;
          }
        });
   },