Puppeteer:for 循环 - 语法问题

Question

我的语法有什么问题？它抛出一个错误：Scraping failed Error: Evaluation failed: ReferenceError: getLogo is not defined代码片段：      const universityAtt = await page.evaluate(() => {            // Getting total number of universities            let totalUniversities = document.querySelector('ul.universities-search-result').childElementCount            for (i = 0; i < totalUniversities; i++) {                getLogo += document.querySelectorAll('.profile_lead > .dp > img.logo-90x90')[i].src;                universityURL += document.querySelectorAll('a.profile.adv, a.profile.basic')[i].href;                let x = [getLogo, universityURL];            };            return x;        });编辑 (1) 当我声明 getLogo 和 universityURL 变量时，        const universityAtt = await page.evaluate(() => {            // Getting total number of universities            let totalUniversities = document.querySelector('ul.universities-search-result').childElementCount            for (i = 0; i < totalUniversities; i++) {                let getLogo += document.querySelectorAll('.profile_lead > .dp > img.logo-90x90')[i].src;                let universityURL += document.querySelectorAll('a.profile.adv, a.profile.basic')[i].href;                let x = [getLogo, universityURL];            };            return x;        });我收到此错误：SyntaxError: Unexpected token '+='    at wrapSafe (internal/modules/cjs/loader.js:1116:16)    at Module._compile (internal/modules/cjs/loader.js:1164:27)    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1220:10)    at Module.load (internal/modules/cjs/loader.js:1049:32)    at Function.Module._load (internal/modules/cjs/loader.js:937:14)    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)    at internal/main/run_main_module.js:17:47

Answer 1

你忘了初始化getLogo，就像你所做的那样totalUniversities

const universityAtt = await page.evaluate(() => {

    let getLogo;

    // Getting total number of universities

    let totalUniversities = document.querySelector('ul.universities-search-result').childElementCount

    for (i = 0; i < totalUniversities; i++) {

        getLogo += document.querySelectorAll('.profile_lead > .dp > img.logo-90x90')[i].src;

        universityURL += document.querySelectorAll('a.profile.adv, a.profile.basic')[i].href;

        let x = [getLogo, universityURL];

    };

    return x;

});

Answer 2

它就在那里说；我看到你赋值但从不声明它们let const或者var请先做这样的事情：

let getLogo += document.querySelectorAll('.profile_lead > .dp > img.logo-90x90')[i].src;

let universityURL += document.querySelectorAll('a.profile.adv, a.profile.basic')[i].href;

Answer 3

请尝试这样。在实际使用它之前定义变量。

let testVar=0;

for (i = 0; i < 10; i++) {

    testVar += 3;

}

console.log(testVar);

Answer 4

您需要定义 getLogo 变量

const universityAtt = await page.evaluate(() => {

            // Getting total number of universities

            

            let totalUniversities = document.querySelector('ul.universities-search-result').childElementCount

            for (i = 0; i < totalUniversities; i++) {

                let getLogo += document.querySelectorAll('.profile_lead > .dp > img.logo-90x90')[i].src;

                universityURL += document.querySelectorAll('a.profile.adv, a.profile.basic')[i].href;

                let x = [getLogo, universityURL];

            };

            return x;

        });