function getUsers(callback) {
  fetch('https://example.com/users', (response) => {
    if (response.status === 200) {
      response.json((data) => {
        callback(data);
      });
    } else {
      console.error('Error fetching users');
    }
  });
}

function getPosts(callback) {
  fetch('https://example.com/posts', (response) => {
    if (response.status === 200) {
      response.json((data) => {
        callback(data);
      });
    } else {
      console.error('Error fetching posts');
    }
  });
}

function getComments(callback) {
  fetch('https://example.com/comments', (response) => {
    if (response.status === 200) {
      response.json((data) => {
        callback(data);
      });
    } else {
      console.error('Error fetching comments');
    }
  });
}

getUsers((users) => {
  console.log(users);
});

getPosts((posts) => {
  console.log(posts);
});

getComments((comments) => {
  console.log(comments);
});

function getUsers() {
  return fetch('https://example.com/users').then((response) => {
    if (response.status === 200) {
      return response.json();
    } else {
      throw new Error('Error fetching users');
    }
  });
}

function getPosts() {
  return fetch('https://example.com/posts').then((response) => {
    if (response.status === 200) {
      return response.json();
    } else {
      throw new Error('Error fetching posts');
    }
  });
}

function getComments() {
  return fetch('https://example.com/comments').then((response) => {
    if (response.status === 200) {
      return response.json();
    } else {
      throw new Error('Error fetching comments');
    }
  });
}

Promise.all([getUsers(), getPosts(), getComments()]).then(([users, posts, comments]) => {
  console.log(users);
  console.log(posts);
  console.log(comments);
}).catch((error) => {
  console.error(error);
});

function limitRequest(urls, limit) {
  let index = 0; // 初始化請(qǐng)求索引為0
  const results = []; // 存儲(chǔ)所有請(qǐng)求的響應(yīng)結(jié)果
  const inProgress = []; // 存儲(chǔ)當(dāng)前正在進(jìn)行的請(qǐng)求

  const executeRequest = (url) => { // 定義執(zhí)行請(qǐng)求的函數(shù)
    const promise = fetch(url).then((response) => response.json()); // 發(fā)起請(qǐng)求并返回一個(gè)Promise對(duì)象
    inProgress.push(promise); // 將Promise對(duì)象添加到inProgress數(shù)組中
    const removeInProgress = () => { // 定義一個(gè)函數(shù)，用于將Promise對(duì)象從inProgress數(shù)組中刪除
      const i = inProgress.indexOf(promise);
      if (i !== -1) {
        inProgress.splice(i, 1);
      }
    };
    promise.then((result) => { // 請(qǐng)求成功的回調(diào)函數(shù)
      removeInProgress(); // 將Promise對(duì)象從inProgress數(shù)組中刪除
      results.push(result); // 將響應(yīng)結(jié)果存儲(chǔ)到results數(shù)組中
      if (index < urls.length) { // 如果還有未完成的請(qǐng)求，繼續(xù)執(zhí)行下一個(gè)請(qǐng)求
        executeRequest(urls[index++]);
      }
    }).catch((error) => { // 請(qǐng)求失敗的回調(diào)函數(shù)
      removeInProgress(); // 將Promise對(duì)象從inProgress數(shù)組中刪除
      console.error(error); // 打印錯(cuò)誤信息
    });
  };

  while (index < limit && index < urls.length) { // 啟動(dòng)最初的一批請(qǐng)求
    executeRequest(urls[index++]);
  }

  return Promise.all(inProgress).then(() => results); // 等待所有請(qǐng)求完成，并返回results數(shù)組的Promise對(duì)象
}