Can't push object into another object, how can I change my code to work with async/await?

问题

I'm having issues trying to work with api "pagination", I need to merge multiple objects into one. However, I can't seem to figure out how to do this with promises and I'm not sure how to work with async/await to get the best results.

I have a class called selly, which works with the Selly API.

getAllProducts(page = 1) {
    return this.makeRequest('products', { page: page });
}
makeRequest(endpoint, params = {}) {
    return axios
        .get(`https://selly.gg/api/v2/${endpoint}`, {
            headers: {
                Authorization: `Basic ${this.genApiToken(this.apiKey, this.apiEmail)}`,
                'User-Agent': `username - localhost`,
            },
            params: params,
        })
        .catch((err) => {
            console.log(err);
        });
}

Which worked great, until I realized I need to fetch multiple pages and combine all of the results into a single object. Here's my attempt:

app.get('/api/products', (req, res) => {
    res.setHeader('Content-Type', 'application/json');
    selly.getAllProducts().then((request) => {
        const pages = request.headers['x-total-pages'];
        let products = request.data;
        if (pages > 1) {
            let i = 2;
            while (pages >= i) {
                selly.getAllProducts(i).then((nextPageRequest) => {
                    nextPageRequest.data.forEach((item) => {
                        products.push(item);
                    });
                });
                i++;
            }
        }
        res.send(JSON.stringify(products));
    });
});

I can't seem to push nextPageRequest to products object. Obviously because res.send runs before the promise selly.getAllProducts(i) is finished.

I understand that the best optimization for this is using async and await, however I just can't get the basic concept of it, or well, at-least how would I refactor my code into using async and await.

How can I get this working?

回答1:

You can make the whole app.get handler async, then await the inital request to figure out how many pages there are, then use a for loop and await additional calls of selly.getAllProducts, pushing the result to the products array. Make sure to try/catch so you can handle errors:

app.get('/api/products', async (req, res) => {
  res.setHeader('Content-Type', 'application/json');
  try {
    const request = await selly.getAllProducts();
    const pages = request.headers['x-total-pages'];
    const products = request.data;
    for (let i = 2; i <= pages; i++) {
      const { data } = await selly.getAllProducts(i);
      products.push(...data);
    }
    res.send(JSON.stringify(products));
  } catch(e) {
    // handle errors
  }
});

来源：https://stackoverflow.com/questions/53992630/cant-push-object-into-another-object-how-can-i-change-my-code-to-work-with-asy

标签

javascript

node.js

ajax

promise

axios