Question

我知道已经有这样的问题。我保证我已经读过它们；我只是不明白。我有一些简单的代码来获取第三方API服务的令牌：

let tok = '';
const getToken = async () => {
  tok = await btt.get();
  console.log(tok);
};
getToken();

tok始终undefined位于console.log。我以为await的全部意思是您的代码将暂停，直到该特定的诺言得到解决或拒绝为止。我误会了吗？这是get函数：

async get () {
  this.paymentGateway.clientToken.generate({
    customerId: '5cdc7405da53494ee0f3bafe'
  }, (err, result) => {
    return new Promise((resolve, reject) => {
      if (result.success) {
        resolve(result.clientToken);
      } else {
        reject(result.errors);
      }
    });
  });
}

我在这个特定问题上停留了一段时间，并尝试了许多不同的方法。如果有人可以提供帮助，我将不胜感激。

谢谢。

Answer 1

您的异步功能未返回承诺。试试这个：

async get () {
  return new Promise((resolve, reject) => {
    this.paymentGateway.clientToken.generate({
      customerId: '5cdc7405da53494ee0f3bafe'
    }, (err, result) => {
      if (result.success) {
        resolve(result.clientToken);
      } else {
        reject(result.errors);
      }
    }
  });
}

一个例子：

const mockPaymentGateway = {
  clientToken: {
    // a mock that will randomly succeed and fail.
    generate: (_, callback) => callback(null, Math.random() > 0.5 ? {
      success: true,
      clientToken: '<This is a token value.>'
    } : {
      errors: ['We have no moneys.']
    }),
  }
}

// I assume you have other things in your service, but here is an example
class SomeService {
  constructor(paymentGateway) {
    this.paymentGateway = paymentGateway;
  }


  async get() {
    return new Promise((resolve, reject) => {
      this.paymentGateway.clientToken.generate({
        customerId: '5cdc7405da53494ee0f3bafe'
      }, (err, result) => {
        if (result.success) {
          resolve(result.clientToken);
        } else {
          reject(result.errors);
        }
      });
    });
  }
}
// Generating mock data...

const btt = new SomeService(mockPaymentGateway);

let tok = '';
const getToken = async() => {
  try {
    tok = await btt.get();
    console.log(tok);
  } catch (e) {
    console.log('Errors getting token:', e);
  }
};

document.querySelector('#get-token').addEventListener('click', async() => {
  console.log('Getting token');
  getToken()
});

<button id="get-token">Get token</button>

Answer 2

在Promise中打个电话：

async get () {
  return new Promise((resolve, reject) => {
    this.paymentGateway.clientToken.generate({
      customerId: '5cdc7405da53494ee0f3bafe'
    }, (err, result) => {
      if (result.success) {
        resolve(result.clientToken);
      } else {
        reject(result.errors);
      }
    });
  });
}

Answer 3

您从未兑现诺言。将最后一行更改为此：

getToken().catch(console.error);

Nodejs变量在“等待”后未定义

3 个答案: