如何在JS异步回调函数中返回值-GAPI

Question

我在应用程序中使用Google的api客户端。我有一个名为的函数initialize，该函数gapi.load用于验证我的凭据并加载youtube api。

gapi.load接受一个回调函数，该函数是I authenticate和loadYoutubeApi异步进行的。我想知道，当我运行initialize函数时，这些异步函数何时完成。我有没有办法在此异步回调函数中返回一个值，以便在调用时知道initialize这些异步任务已完成？谢谢！

const apiKey = 'my-api-key';
const clientId = 'my-client-id';

const authenticate = async () => {
  const { gapi } = window;
  try {
    await gapi.auth2.init({ clientId });
    console.log('authenticated');
  } catch (error) {
    throw Error(`Error authenticating gapi client: ${error}`);
  }
};

const loadYoutubeApi = async () => {
  const { gapi } = window;
  gapi.client.setApiKey(apiKey);
  try {
    await gapi.client.load('https://www.googleapis.com/discovery/v1/apis/youtube/v3/rest');
    console.log('youtube api loaded');
  } catch (error) {
    throw Error(`Error loading youtube gapi client: ${error}`);
  }
};

const initialize = async () => {
  const { gapi } = window;
  const isInitialized = await gapi.load('client:auth2', async () => {
    try {
      await authenticate();
      await loadYoutubeApi();
      return true;
    } catch (error) {
      throw Error(`Error initializing gapi client: ${error}`);
    }
  });
  console.log(isInitialized); // expects `true` but am getting `undefined`
};

initialize();

Answer 1

将负载包装在Promise中，以便您可以像其余代码一样等待它。

try {
  await new Promise((resolve,reject) => {
    gapi.load('client:auth2', resolve);
  });
  await authenticate();
  await loadYoutubeApi();
} catch (error) {
  throw Error(`Error initializing gapi client: ${error}`);
}
//is Initialized

Answer 2

您可以将gapi.load一部分包装在 Promise 中，如下所示：

const initialize = async () => {
  const { gapi } = window;
  await new Promise((resolve, reject) => {
    gapi.load('client:auth2', async () => {
      try {
        await authenticate();
        await loadYoutubeApi();
        resolve();
      } catch (error) {
        throw Error(`Error initializing gapi client: ${error}`);
      }
    });
  });
  return true;
};

initialize(); // returns 'true' when done.