Node.js Promises 返回某些元素未定义，我做错了什么或者我可以改进什么？

Question

我的一些承诺返回“未定义”，我看不出我做错了什么。 尝试添加超时但没有解决它，我仍在学习并努力发现我的错误。

看起来像是 scrapeSpecificOperatorStats 块上的问题，但是一些回报很好。

示例： 期待：

  {
    name: 'Kapkan',
    imageUrl: 'https://staticctf.ubisoft.com/J3yJr34U2pZ2Ieem48Dwy9uqj5PNUQTn/7MofnDHeL1uwsenBVjxplQ/1e5af8fe9cf6f36516c7f6e5d56fcac0/r6-operators-list-kapkan.png',
    linkUrl: 'https://www.ubisoft.com/en-us/game/rainbow-six/siege/game-info/operators/kapkan',
    operatorStats: { specialty: 'ANTI-ENTRY, TRAPPER' }
  }

实际：

  {
    name: 'Kapkan',
    imageUrl: 'https://staticctf.ubisoft.com/J3yJr34U2pZ2Ieem48Dwy9uqj5PNUQTn/7MofnDHeL1uwsenBVjxplQ/1e5af8fe9cf6f36516c7f6e5d56fcac0/r6-operators-list-kapkan.png',
    linkUrl: 'https://www.ubisoft.com/en-us/game/rainbow-six/siege/game-info/operators/kapkan',
    operatorStats: undefined
  }

问题仅出现在 operatorStats 上并且仅针对某些元素

我的代码：

const axios = require("axios");
const cheerio = require("cheerio");

// Define the URL of the webpage
const url = "https://www.ubisoft.com/en-us/game/rainbow-six/siege/game-info/operators";

// Define a function to scrape the operator stats from the link URL
const scrapeSpecificOperatorStats = async (link) => {
  try {
    // Make a HTTP request to the webpage
    const response = await axios.get(link);

    // Load the HTML content into Cheerio
    const $ = cheerio.load(response.data);

    // Find and Extract the operator specialty
    const specialty = $("span.operator__header__roles").text();

    // Return the results
    return { specialty };
  } catch (error) {
    console.error(error);
  }
};

// Define a function to scrape the operator stats
const scrapeOperatorStats = async (url) => {
  try {
    // Make a HTTP request to the webpage
    const response = await axios.get(url);

    // Load the HTML content into Cheerio
    const $ = cheerio.load(response.data);

    // Find the element that contains the operator stats
    const statsElement = $(".oplist__card");

    // Create an array of promises for each operator stat element
    const statsPromises = statsElement.map(async (index, element) => {
      // Extract the operator name, specialty, and description
      const name = $(element).find("span").text();

      // Extract the image URL and link URL
      const imageUrl = $(element).find("img").attr("src");
      const linkUrl = "https://www.ubisoft.com" + $(element).attr("href");

      // Get the operator stats
      const operatorStats = await scrapeSpecificOperatorStats(linkUrl);

      // Return the result
      return {
        name,
        imageUrl,
        linkUrl,
        operatorStats,
      };
    });

    // Wait for all promises to resolve and return the results
    return Promise.all(statsPromises);
  } catch (error) {
    console.error(error);
  }
};

// Call the function and log the results
scrapeOperatorStats(url)
  .then((results) => console.log(results))
  .catch((error) => console.error(error));

Answer 1

问题是，当发生错误时，

scrapeSpecificOperatorStats

返回

undefined

，因为你有一个

try

/

catch

，而

catch

只是注销错误。这意味着执行会从函数末尾开始，隐式返回

undefined

。

要修复此问题，要么允许

scrapeSpecificOperatorStats

中的错误传播，而不是将其转换为

undefined

（通过删除

try

/

catch

）并在更高级别处理它们（例如在

scrapeOperatorStats

中），或者处理发生错误时

scrapeSpecificOperatorStats

返回

undefined

的事实。最好的选择通常是前者；过早处理错误是一种常见的反模式。