封装函数：

const { ErrorModel } = require("../model/resModel");
function schema(method, schemas) {
  async function validateSchema(ctx, next) {
    let data = null;
    if (method === "get") {
      data = await ctx.request.query;
    } else {
      data = await ctx.request.body;
    }
    const { error } = schemas.validate(data);
    if (error) {
      ctx.body = new ErrorModel(error.message);
      return;
    }
    await next();
  }

  return validateSchema;
}
module.exports = schema;

规则：

/**
 * string() 值必须是字符串
 * alphanum() 值只能是包含 a-zA-Z0-9 的字符串
 * min(length) 最小长度
 * max(length) 最大长度
 * required() 值是必填项，不能为 undefined
 * pattern(正则表达式) 值必须符合正则表达式的规则
 */
const Joi = require("joi");

const user = Joi.object({
  username: Joi.string().alphanum().min(1).max(10).required(),
  password: Joi.string()
    .pattern(/^[\S]{6,12}$/)
    .required()
});

module.exports = {
  user
};

路由：

const Router = require("koa-router");
const { regUser, blogList, login } = require("../controllers/user");
const schema = require("../model/schema");
// 导入 Joi 来定义验证规则
const { user } = require("../schema/user");
// const upload = require("../model/upload");
const router = new Router({ prefix: "/api/user" });
// 查询博客信息
router.get("/bloglist", blogList);
// 注册
router.post("/reguser", schema("post", user), regUser);
// 上传头像
// router.post("/upload", upload.single("avatar"), ctx => {
//   console.log("ctx.request.file", ctx.request.file);
//   console.log("ctx.file", ctx.file.path);
//   console.log("ctx.request.body", ctx.request.body);
//   ctx.body = "done";
// });
// 登录
router.post("/login", login);
module.exports = router;