javascript - meteor JS : Handling an async function inside another async function?

Question

所以，我不知道如何正确处理这个问题。

我想做的是:

// client side
Meteor.call("getData", url, function(images) {
  console.log(images); // get array of image src
});

// server side
Meteor.methods({
  "getData": (url) => {
      var images = [];
     // here is where I am lost
     // scrape the images
     scrape.request(url, function(err, $) {
       if (!err) {
          $('img').each(function(img) {
            let src = img.attribs.src;
            images.push(src);
          }
          // so at this point, I can console log an array on the server, but I need to bring it back to the client
       }
     } // now, how do I push all these and then signal to return the array?
   return images; // returns undefined, not waiting for all the data
   // I'm not sure how to wait for the array to be updated.
}});

想法？

所以，回顾一下，我想获取从传递给 Meteor 方法的网站中抓取的所有图像源的数组。

Answer 1

有一个很好的tutorial上Meteor.wrapAsync这说明了这一点。另外this previous answer提供更多详细信息并解释错误处理。

所有操作都发生在服务器上。对于您的情况:

Meteor.methods({
  getData(url) => {
    const syncScrape = Meteor.wrapAsync(scrape.request);
    try {
      const $ = syncScrape(url,{});
      let images = [];
      $('img').each(img => {
        images.push(img.attribs.src);
      });
      return images;
    }
    catch(error) {
      throw new Meteor.error(error);
    }
  }
});

您的客户端调用还需要包含回调中的错误:

Meteor.call("getData", url, (error, images) => {
  if (!error) console.log(images); // get array of image src
});