暴露的函数 querySelector 在 Puppeteer 中不起作用 [英] Exposed function querySelector not working in Puppeteer

问题描述

document.querySelectorAll('.summary').innerText;

这会在下面的代码片段中引发错误，指出document.querySelector 不是函数"；在我的 Puppeteer 页面的公开功能 docTest 中.

This throws an error in the below snippet saying "document.querySelector is not a function" in my Puppeteer page's exposed fucntion docTest.

我想将特定节点传递给每个方法并在 evaluate 中获取结果.

I want to pass a specific node to each method and get the result inside evaluate.

与 document.getElemnetbyId 相同.

const puppeteer = require('puppeteer');
//var querySelectorAll = require('query-selector');


let docTest = (document) => {
var summary = document.querySelectorAll(.summary).innerText;
console.log(summary);
return summary;
}

let scrape = async () => {

const browser = await puppeteer.launch({
    headless: false
});
const page = await browser.newPage();

await page.goto('http://localhost.com:80/static.html');
await page.waitFor(5000)
await page.exposeFunction('docTest', docTest);

var result = await page.evaluate(() => {
    var resultworking = document.querySelector("tr");
    console.log(resultworking);
    var summary  = docTest(document);
    console.log(resultworking);
    return summary;

});
console.log(result);

await page.waitFor(7000);
browser.close();
return {
    result
}
};

scrape().then((value) => {
console.log(value); // Success!
});

推荐答案

我刚刚遇到了同样的问题.问题是 page.evaluate() 函数回调必须是一个 async 函数并且你的函数 docTest() 将返回一个 Promise 在 page.evaluate() 内部调用时.要修复它，只需将 async 和 await 关键字添加到您的代码中:

I just had the same question. The problem is that the page.evaluate() function callback has to be an async function and your function docTest() will return a Promise when called inside the page.evaluate(). To fix it, just add the async and await keywords to your code:

await page.exposeFunction('docTest', docTest);

var result = await page.evaluate(async () => {
    var summary = await docTest(document);
    console.log(summary);
    return summary;
});

只要记住 page.exposeFunction() 会让你的函数返回一个 Promise，然后，你需要使用 async 和 等待.发生这种情况是因为您的函数不会在浏览器中运行，但在您的 nodejs 应用程序中.

Just remember that page.exposeFunction() will make your function return a Promise, then, you need to use async and await. This happens because your function will not be running inside your browser, but inside your nodejs application.

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