确保信任：Promise在服务领域的应用案例

function checkUsername(username) {
  return new Promise((resolve, reject) => {
    // 异步操作，检查用户名是否已存在
    setTimeout(() => {
      if (用户名已存在)
        reject("用户名已存在");
      else
        resolve();
    }, 1000);
  });
}

function createUser(username, password) {
  return new Promise((resolve, reject) => {
    // 异步操作，创建用户
    setTimeout(() => {
      // 业务逻辑...
      resolve();
    }, 1000);
  });
}

function sendEmail(username) {
  return new Promise((resolve, reject) => {
    // 异步操作，发送邮件
    setTimeout(() => {
      // 业务逻辑...
      resolve();
    }, 1000);
  });
}

checkUsername("testuser")
  .then(() => createUser("testuser", "123456"))
  .then(() => sendEmail("testuser"))
  .then(() => {
    console.log("注册成功");
  })
  .catch((error) => {
    console.error("注册失败：" + error);
  });

function checkStock(order) {
  return new Promise((resolve, reject) => {
    // 异步操作，检查库存
    setTimeout(() => {
      // 业务逻辑...
      if (库存充足)
        resolve();
      else
        reject("库存不足");
    }, 1000);
  });
}

function payOrder(order) {
  return new Promise((resolve, reject) => {
    // 异步操作，支付订单
    setTimeout(() => {
      // 业务逻辑...
      resolve();
    }, 1000);
  });
}

function shipOrder(order) {
  return new Promise((resolve, reject) => {
    // 异步操作，发货
    setTimeout(() => {
      // 业务逻辑...
      resolve();
    }, 1000);
  });
}

checkStock(order)
  .then(() => payOrder(order))
  .then(() => shipOrder(order))
  .then(() => {
    console.log("订单处理完成");
  })
  .catch((error) => {
    console.error("订单处理出错：" + error);
  });