koa2 数据api中间件设计模型的实现方法

module.exports = async (ctx, next) => {
 ctx.share_data.api_data = await axios.get('/api');

 await next();
};

module.exports = async (ctx, next) => {
 ctx.share_data.db_data = await mysql_query('SELECT XXX').catch(() => {});

 await next();
};

const api = require('api.js');
const db = require('db.js');
          
app.get('/get-api', api, (ctx) => ctx.body = ctx.share_data);
app.get('/get-db', db, (ctx) => ctx.body = ctx.share_data);
app.get('/get-api-and-db', api, db, (ctx) => ctx.body = ctx.share_data);

module.exports = (middleware = []) => {
 if (!Array.isArray(middleware)) throw new TypeError('Middleware stack must be an array!');
 for (const fn of middleware) {
  if (typeof fn !== 'function') throw new TypeError('Middleware must be composed of functions!');
 }

 return async (context = {}, next = f => f) => {
  await Promise.all(
   middleware.map(middleware => {
    return new Promise((rs, rj) => {
     middleware(context, () => Promise.resolve())
      .then(rs)
      .catch(rj);
    });
   }),
  );

  await next();
 };
};

const api = require('api.js');
const db = require('db.js');
const superCompose = require('super-compose.js');
          
app.get('/get-api-and-db', superCompose([api, db]), (ctx) => ctx.body = ctx.share_data);

module.exports = async (ctx, next) => {
 if (ctx.share_data.api_data) {
  return await next();
 }

 ctx.share_data.api_data = await axios.get('/api');

 await next();
};

const api = require('api.js');

module.exports = compose([
 api,
 async (ctx, next) => {
  const { api_data: { api_data: { id = 0 } = {} } = {} } = ctx;

  if (id < 0) {
   await next();
  } else {
   ctx.api_data.api_1_data = await axios.get('/api', { params: { id } });
  }

  await next();
 },
])

const api_1 = require('api_1.js');
const db = require('db.js');
const superCompose = require('super-compose.js');
          
app.get('/get-api-and-db', superCompose([api_1, db]), (ctx) => ctx.body = ctx.share_data);

module.exports = async (ctx, next) => {
 const { break_list = [] } = ctx;


 if (break_list.includes('api_data')) {
  // 可能会误伤其他组合引用该中间件的情况。
  // 如可能会误伤，可加上。
  // ctx.break_list = break_list.filter(v => v !== 'api_data')
  return await next();
 } else {
  ctx.share_data.api_data = await axios.get('/api');
 }

 await next();
}

const api = require('api.js');
const db = require('db.js');
const superCompose = require('super-compose.js');
          
app.get(
 '/get-api-and-db',
 async (ctx, next) => {
  ctx.break_list = ['api_data'];
  await next();
 },
 superCompose([api, db]),
 ctx => (ctx.body = ctx.share_data)
);

const api = require('api.js');
const db = require('db.js');
const superCompose = require('super-compose.js');
const compost = rquire('koa-compose')

const babala = compose([
 superCompose([api, db]),
 async (ctx, next) => {
  const {
   share_data: { api_data: { id = 0 } = {}, db_data: { title } = {} } = {},
  } = ctx;

  ctx.body = { id, title };
  // OR
  // ctx.share_data.babala = {}
 },
]);

app.get(
 '/get-api-and-db',
 babala
);

app.get('/api', async ctx => {
 const api_1 = await axios.get('/api_1');
 await api_2 = await axios.get('/api_2');

 // ...
 // ...
 // 这里有一百行
 // ... 
 
 const [api_3, api_4] = await new Promise.all([axios.get('/api_3'), axios.get('/api_4')]);
 
 // ...
 // ...
 // 这里有几百行
 // ...

 ctx.body = {};
});