以邮箱校验为例：

1.【validate.js】中自定义邮箱验证规则

/* 电子邮箱校验 */
export function validateEmail(str) {
  const reg = /^[A-Za-z0-9\u4e00-\u9fa5]+@[a-zA-Z0-9_-]+(\.[a-zA-Z0-9_-]+)+$/
  return reg.test(str)
}

2.在<script>标签中引入外部邮箱验证规则【import { validateEmail } from "../assets/js/validate.js"】

const：定义一个规则常量，常量名可变，【= (rule, value, callback) => {}】为固定格式，【value】 为验证的字段值

<script>
import axios from "axios";
// 引入了外部的验证规则
import { validateEmail } from "../assets/js/validate.js";

// 判断邮箱是否正确
const validatorEmail = (rule, value, callback) => {
  if (!value) {
    return callback(new Error("邮箱不能为空"));
  } else {
    if (validateEmail(value)) {
      callback();
    } else {
      return callback(new Error('邮箱格式不正确'))
    }
  }
};

export default {
  name: "login",
  data() {
    return {
      activeName: "login",
      checked: false,
      user: {
        username: "",
        password: ""
      },
      // 通过 formRules 属性传入约定的验证规则
      formRules: {
        username: [{ required: true, message: "用户名不能为空", trigger: "blur" }],
        password: [
          { required: true, message: "密码不能为空", trigger: "blur" },
          { type: 'string', min: 6, message: '密码不能小于6位', trigger: 'blur' }
        ],
        email: [{ required: true, validator: validatorEmail, trigger: "blur" }]
      },

    };

  },
}