合并一个对象的所有forEach

const obj = {
  a: [1, 2, 3],
  b: [4, 5, 6],
  c: [7, 8, 9]
};

const promises = [];

Object.keys(obj).forEach(key => {
  const promise = obj[key].forEach(value => {
    // 执行异步操作，例如：
    return new Promise((resolve) => {
      setTimeout(() => {
        console.log(`Value: ${value}`);
        resolve();
      }, 1000);
    });
  });
  promises.push(promise);
});

Promise.all(promises).then(() => {
  console.log('All forEach loops have completed.');
});

const obj = {
  a: [1, 2, 3],
  b: [4, 5, 6],
  c: [7, 8, 9]
};

for (const key of Object.keys(obj)) {
  obj[key].forEach(value => {
    console.log(`Value: ${value}`);
    // 执行同步操作
  });
}

console.log('All forEach loops have completed.');