在Chrome+Puppeeter的evaluate（）上下文中有没有添加脚本添加新函数的方法？

Question

例如，包含一个具有帮助函数x的文件来调用Xpath函数:x('//a/@href')

Answer 1

您可以在单独的页中注册helper函数。evaluate()函数。page.exposeFunction()看起来很诱人，但它不能访问浏览器上下文（您需要document对象）。

下面是一个使用$x()注册帮助器函数的示例：

const puppeteer = require('puppeteer');

const helperFunctions = () => {
    window.$x = xPath => document
        .evaluate(
            xPath,
            document,
            null,
            XPathResult.FIRST_ORDERED_NODE_TYPE,
            null
        )
        .singleNodeValue;
};

(async () => {
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto('https://en.wikipedia.org', { waitUntil: 'networkidle2' });

    await page.evaluate(helperFunctions);

    const text = await page.evaluate(() => {
        // $x() is now available
        const featureArticle = $x('//*[@id="mp-tfa"]');

        return featureArticle.textContent;
    });
    console.log(text);
    await browser.close();
})();

（编辑-从文件中添加帮助程序）

window.$x = xPath => document
    .evaluate(
        xPath,
        document,
        null,
        XPathResult.FIRST_ORDERED_NODE_TYPE,
        null
    )
    .singleNodeValue;

const puppeteer = require('puppeteer');

(async () => {
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto('https://en.wikipedia.org', { waitUntil: 'networkidle2' });

    await page.addScriptTag({ path: './helperFunctions.js' });

    const text = await page.evaluate(() => {
        // $x() is now available
        const featureArticle = $x('//*[@id="mp-tfa"]');

        return featureArticle.textContent;
    });
    console.log(text);
    await browser.close();
})();