Nodejs 变量在“await”之后未定义

Question

我知道已经有这样的问题了。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 3 方 API 服务的令牌：

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

tok总是undefined在console.log. 我认为重点await是你的代码会暂停，直到特定的承诺得到解决或拒绝；我错了吗？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);
      }
    });
  });
}

我已经被这个特定问题困扰了一段时间，并尝试了很多不同的方法。如果有人可以提供帮助，我将不胜感激。

谢谢。

Answer 1

您的异步函数没有返回承诺。尝试这个：

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：

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);
      }
    }
  });
}

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()
});