如何在Koa中执行条件路由器？

const Koa = require('koa');
const Router = require('koa-router');
const app = new Koa();
const router = new Router();

const conditionRouter = async (ctx, next) => {
  // 获取请求的条件
  const condition = ctx.request.query.condition;

  // 根据条件执行相应的路由处理程序
  if (condition === 'A') {
    await handleRouteA(ctx);
  } else if (condition === 'B') {
    await handleRouteB(ctx);
  } else {
    await next(); // 继续执行下一个中间件或路由
  }
};

const handleRouteA = async (ctx) => {
  // 处理条件A的路由请求
  ctx.body = 'This is route A';
};

const handleRouteB = async (ctx) => {
  // 处理条件B的路由请求
  ctx.body = 'This is route B';
};

app.use(conditionRouter);

router.get('/', async (ctx) => {
  ctx.body = 'Hello, Koa!';
});

app.use(router.routes());

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});