Sample code for implementing form validation with pure CSS

<el-form :model="numberValidateForm" ref="numberValidateForm" label-width="100px" class="demo-ruleForm">
  <el-form-item
    label="Age"
    prop="age"
    :rules="[
      {required: true, message: 'Age cannot be empty'},
      { type: 'number', message: 'Age must be a numeric value'}
    ]"
  >
    <el-input type="age" v-model.number="numberValidateForm.age" autocomplete="off"></el-input>
  </el-form-item>
  <el-form-item>
    <el-button type="primary" @click="submitForm('numberValidateForm')">Submit</el-button>
    <el-button @click="resetForm('numberValidateForm')">Reset</el-button>
  </el-form-item>
</el-form>
<script>
  export default {
    data() {
      return {
        numberValidateForm: {
          age: ''
        }
      };
    },
    methods: {
      submitForm(formName) {
        this.$refs[formName].validate((valid) => {
          if (valid) {
            alert('submit!');
          } else {
            console.log('error submit!!');
            return false;
          }
        });
      },
      resetForm(formName) {
        this.$refs[formName].resetFields();
      }
    }
  }
</script>

/*
 * css
 */
 :root {
 	--error-color: red;
 }
 .form > input {
 	margin-bottom: 10px;
 }
 .form > .f-tips {
 	color: var(--error-color);
 	display: none;
 }
 input[type="text"]:invalid ~ input[type="submit"],
 input[type="password"]:invalid ~ input[type="submit"] {
 	display: none;
 }
 input[required]:invalid + span {
 	display: inline;
 }
 
 /*
  *html
  */
<form class="form" id="form" method="get" action="/api/form">
    account:
    <input data-title="Account" pattern="[\w]{6,10}" name="account" type="text" required />
    <span class="f-tips">Please enter the correct account number</span>
    <br />
    password:
    <input data-title="Password" pattern="[\w]{6,10}" name="password" type="password" required />
    <span class="f-tips">Please enter the correct password</span>
    <br />
    <input name="button" type="submit" value="Submit" />
</form>

<input data-title="Account" pattern="/[\w]{6, 10}/" name="account" type="text" required />

<input data-title="Account" pattern="/\w{6,10}/" name="account" type="text" required />