实现 如果上一次的没请求完，之后的就无响应

[Sunny-117]

[AaronKevinAA]

let runningTask = 0; async function callAsyncFunction(promiseFn) { if(runningTask===0){ console.log("Calling async function..."); runningTask++; // 将 promiseFn 包装成一个新的 Promise，以便可以在其执行完毕后进行下一步操作 // 返回当前的 promise，以便可以在外部处理其结果 return new Promise(async (resolve, reject) => { try { // await不会捕获错误，所以用try...catch const result = await promiseFn(); resolve(result); runningTask--; } catch (err) { reject(err); runningTask--; } }); }else{ return null; } }

[JeromeD3]

let isRequesting = false

function myRequest(url) { if (isRequesting) { return Promise.reject('请求中') }

isRequesting = true return fetch(url) .then((res) => { isRequesting = false return res.json() }) .catch((err) => { isRequesting = false throw err }) }

myRequest('https://jsonplaceholder.typicode.com/todos/1') .then((res) => { console.log(res) }) .catch((err) => { console.log(err) })

myRequest('https://jsonplaceholder.typicode.com/todos/5') .then((res) => { console.log(res) }) .catch((err) => { console.log(err) })

myRequest('https://jsonplaceholder.typicode.com/todos/4') .then((res) => { console.log(res) }) .catch((err) => { console.log(err) })

myRequest('https://jsonplaceholder.typicode.com/todos/3') .then((res) => { console.log(res) }) .catch((err) => { console.log(err) })

myRequest('https://jsonplaceholder.typicode.com/todos/2') .then((res) => { console.log(res) }) .catch((err) => { console.log(err) })

[AgneseLee]

function promiseWrapper(fetchApi) { let oldReqPromise = Promise.resolve(); const doRequest = () => { const newReqPromise = oldReqPromise.then(() => { return new Promise((resolve, reject) => { setTimeout(() => { resolve("data"); }, 1000); }); }); oldReqPromise = newReqPromise; return newReqPromise; }; return doRequest; }

// 测试用例 const request = promiseWrapper();

request().then(() => { console.log("第一次请求完成"); });

request().then(() => { console.log("第二次请求完成"); });

setTimeout(() => { request().then(() => { console.log("第三次请求完成"); }); }, 1500);

[tyust512]

是不是考promise的链式执行？

[topulikeweb]

// 使用调度器实现，控制并发为1
class Scheduler {
  constructor (maxTask) {
    // 最大并发量
    this.maxTask = maxTask
    // 任务队列
    this.queue = []
    // 当前执行任务的数量
    this.currentTask = 0
  }
  
  // 添加任务
  addTask (task) {
    return new Promise((resolve, reject) => {
      this.queue.push({
        task,
        resolve,
        reject
      })
      this.runTask()
    })
  }
  
  // 执行任务
  runTask () {
    // 未达到最大并发量
    while (this.currentTask < this.maxTask && this.queue.length > 0) {
      const { task, resolve, reject } = this.queue.shift()
      // 当前执行的任务
      this.currentTask++
      task().then(resolve, reject).finally(() => {
        this.currentTask--
        this.runTask()
      })
    }
  }
}

// 示例任务函数
function createTask (time) {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve();
    }, time);
  });
}

// 创建调度器实例，设置并发数为2
const scheduler = new Scheduler(1);

function add (time, name) {
  scheduler.addTask(() => createTask(time)).then(() => {
    console.log(name)
  })
}

add(1000, 1)
add(1000, 2)
add(1000, 3)