promise js 例子

// 创建一个 Promise 对象
const fetchData = () => {
  return new Promise((resolve, reject) => {
    // 模拟异步操作，例如网络请求
    setTimeout(() => {
      const data = { message: 'Data fetched successfully' };
      // 模拟成功情况
      resolve(data);
      // 如果失败，可以使用 reject(new Error('Failed to fetch data'));
    }, 2000);
  });
};

// 使用 Promise
fetchData()
  .then((data) => {
    console.log(data.message); // 输出: Data fetched successfully
  })
  .catch((error) => {
    console.error(error.message); // 如果有错误，会在这里捕获
  });

fetchData()
  .then((data) => {
    console.log(data.message);
    // 模拟一个错误
    throw new Error('Something went wrong');
  })
  .catch((error) => {
    console.error(error.message); // 输出: Something went wrong
  });

const fetchData1 = () => new Promise((resolve) => setTimeout(() => resolve('Data 1'), 1000));
const fetchData2 = () => new Promise((resolve) => setTimeout(() => resolve('Data 2'), 1500));

Promise.all([fetchData1(), fetchData2()])
  .then((results) => {
    console.log(results); // 输出: ['Data 1', 'Data 2']
  })
  .catch((error) => {
    console.error(error.message);
  });