问关于节点回调函数的功能和如何访问
EN

Stack Overflow用户

提问于 2022-07-31 10:58:14

回答 1查看 100关注 0票数 0

我有一个API的初学者代码，它允许我搜索一个术语，比如Apple，并将JSON对象的列表打印到控制台。

var params = {
  q: "Apple",
  tbm: "isch",
  ijn: "0"
};
                  
var callback = function(data) {
  console.log(data["images_results"]);
};
                
src.json(params, callback);

我希望将数据“images_results”项保存到变量中，而不是打印到控制台。到目前为止，我已经尝试在回调函数中将var设置为数据“images_results”(不过，var是在函数之外初始化的)，在另一种情况下，我将其设置为src.json(params，回调)。但是当我试图访问变量时，它显示为未定义的。如何使用这个API访问数据“images_results”而不是将结果打印到控制台？

var a;

var params = {
  q: "Apple",
  tbm: "isch",
  ijn: "0"
};
                  
var callback = function(data) {
  a = data["images_results"];
};
                
src.json(params, callback);

console.log(a);

更新的

const params = {
            engine: "google",
            google_domain: "google.com",
            hl: "en",
            gl: "us",
            device: "desktop",
            tbm: "isch",
        };

        const getJson = async () => {
            return new Promise((resolve) => {
              src.json(params, resolve);
            });
        };

        const getFirstImages = async () => {
            const imres = [];
            for (item in items) {
              params.q = item['sku'];
              const json = await getJson();
              imres.push(json.images_results[0]["original"]);
            }
            return imres;
          };

          getFirstImages().then(imres => {
            console.log(imres);
            images = imres;
            myCache.set('total_images', images);
        })

node.js

callback

回答 1

Stack Overflow用户

回答已采纳

发布于 2022-08-01 01:00:22

您无法以这种方式保存SerpApi的结果，因为.json方法是异步的，并且在控制台中打印a之后运行callback函数。您只需要在某些函数中处理结果，因为不能在全局范围内使用类似于await的东西。如果你能更多地告诉我你下一步想做些什么，我可以帮你更好。但现在你可以做这样的事：

var params = {
  q: "Apple",
  tbm: "isch",
  ijn: "0"
};
                  
var callback = function(data) {
  var a = data["images_results"];
  
  // do what you want to do next in this function
};
                
src.json(params, callback);

或者您可以使用.then链接：

const params = {
  q: "Apple",
  tbm: "isch",
  ijn: "0"
};

const getJson = () => {
  return new Promise((resolve) => {
    src.json(params, resolve);
  });
};

getJson().then(({images_results}) => {
  var a = images_results
  // do what you want to do next in this function
});

更新：

如果我理解得对，您需要做(签入在线IDE)这样的事情：

const SerpApi = require("google-search-results-nodejs");
const src = new SerpApi.GoogleSearch(process.env.API_KEY); //your api key from serpapi.com

const params = {
  engine: "google",
  google_domain: "google.com",
  hl: "en",
  gl: "us",
  device: "desktop",
  tbm: "isch",
};

const searchQueries = ["apple", "cherry", "banana"];

const getJson = async () => {
  return new Promise((resolve) => {
    src.json(params, resolve);
  });
};

const getFirstImages = async () => {
  const images = [];
  for (query in searchQueries) {
    params.q = query;
    const json = await getJson();
    images.push(json.images_results[0]);
  }
  return images;
};

getFirstImages().then(images => {
    console.log(images)
    // or do what you want to do next
})

请注意，我们在异步函数getFirstImages中用图像填充数组，等待(await)接收带有结果的对象(json)。另外，您不能使用数组方法(例如forEach)在searchQueries上迭代，因为await不能工作。

输出：

[
   {
      "position":1,
      "thumbnail":"https://serpapi.com/searches/62e7affb9bddf73501bfde87/images/d6db51527c0e83ba92158999bf4cd1063f03d4fcbdfbcca0bb5f77b191b27a53.png",
      "source":"en.wiktionary.org",
      "title":"0 - Wiktionary",
      "link":"https://en.wiktionary.org/wiki/0",
      "original":"https://upload.wikimedia.org/wikipedia/commons/thumb/6/6e/Z%C3%A9ro.svg/1200px-Z%C3%A9ro.svg.png",
      "is_product":false
   },
   {
      "position":1,
      "thumbnail":"https://serpapi.com/searches/62e7affed737d7249d50f729/images/920c4e458460303dc0bb77ec3f448f9ad3946e5412eb72ca3cbb8751a8cee7c6.png",
      "source":"en.wiktionary.org",
      "title":"1 - Wiktionary",
      "link":"https://en.wiktionary.org/wiki/1",
      "original":"https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Un1.svg/1200px-Un1.svg.png",
      "is_product":false
   },
   {
      "position":1,
      "thumbnail":"https://serpapi.com/searches/62e7b0064055aa23fb85ce10/images/4036a5ed1a2cf55b31ca73fd5c660dc71431f02052cf7ee6f4796043060b475c.png",
      "source":"en.wiktionary.org",
      "title":"2 - Wiktionary",
      "link":"https://en.wiktionary.org/wiki/2",
      "original":"https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Deux.svg/1200px-Deux.svg.png",
      "is_product":false
   }
]