手写算法模拟KOA

// 实现 洋葱模型类 App，打印a,b,c,C,B,A
class App {
  constructor() {
    this.tasks = []
    this.ctx = null
  }
  use(fn) {
    this.tasks.push(fn)
  }
  async run() {
    const ctx = this.ctx
    async function loop(tasks) {
      const fn = tasks.shift()
      if (fn) {
        await fn(ctx, () => {
          loop(tasks)
        })
      }
    }
    loop(this.tasks)
  }
}


// 测试
const app = new App();
app.use((_, next) => {
  console.log("a");
  next();
  console.log("A");
});

app.use((_, next) => {
  console.log("b");
  next();
  console.log("B");
});

app.use((_, next) => {
  console.log("c");
  next();
  console.log("C");
});

app.run();