传递给 page.evaluate 的变量未定义

Question

当我使用page.evaluate并将变量传递给它时，它们是未定义的。let reaction;// First console.log actually logs the string as expectedconsole.log(reactionTitle);await this.page.evaluate(function (reactionTitle, reaction) {    // Second console.log logs undefined in the website's console    console.log(reactionTitle);    document.querySelectorAll('span.embedAuthorName-3mnTWj').forEach(s => {        // Third console.log logs all innerTexts in the website's console        console.log(s.innerText)        if (s.innerText == reactionTitle) {            console.log(s);            reaction = s.offsetParent.offsetParent.querySelector('.container-1ov-mD').querySelector('.reactions-12N0jA').querySelector('div').querySelector('.reaction-1hd86g').querySelector('.reactionInner-15NvIl');            console.log(reaction)        }    });}, (reactionTitle, reaction));console.log(reaction)我在代码中添加了一些注释以显示未定义反应标题的位置。

Answer 1

从(reactionTitle, reaction)in 参数中删除括号：

await this.page.evaluate((reactionTitle, reaction) => { ... }, reactionTitle, reaction)

或者

await this.page.evaluate(({reactionTitle, reaction}) => { ... }, {reactionTitle, reaction})

page.evaluate在页面上下文中执行，并且与 puppeteer 执行环境分开。我建议看一下文档和架构。要从 puppeteer 中的页面内上下文访问变量，您需要返回变量。请注意，变量必须是可序列化的：

const result = await this.page.evaluate(({reactionTitle, reaction}) => { 

    ... 

    return reaction;

}, {reactionTitle, reaction});

如果返回值是页内对象，请使用evaluateHandle.