如何将变量传递给评估函数? [英] How can I pass variable into an evaluate function?

问题描述

我正在尝试将一个变量传递给 Puppeteer，但是当我使用以下非常简化的示例时，变量 evalVar 未定义.

I'm trying to pass a variable into a page.evaluate() function in Puppeteer, but when I use the following very simplified example, the variable evalVar is undefined.

我是 Puppeteer 的新手，找不到任何示例来构建，所以我需要帮助将该变量传递到 page.evaluate() 函数，以便我可以在内部使用它.

I'm new to Puppeteer and can't find any examples to build on, so I need help passing that variable into the page.evaluate() function so I can use it inside.

const puppeteer = require('puppeteer');

(async() => {

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

  const evalVar = 'WHUT??';

  try {

    await page.goto('https://www.google.com.au');
    await page.waitForSelector('#fbar');
    const links = await page.evaluate((evalVar) => {

      console.log('evalVar:', evalVar); // appears undefined

      const urls = [];
      hrefs = document.querySelectorAll('#fbar #fsl a');
      hrefs.forEach(function(el) {
        urls.push(el.href);
      });
      return urls;
    })
    console.log('links:', links);

  } catch (err) {

    console.log('ERR:', err.message);

  } finally {

    // browser.close();

  }

})();

推荐答案

您必须像这样将变量作为参数传递给 pageFunction:

You have to pass the variable as an argument to the pageFunction like this:

const links = await page.evaluate((evalVar) => {

  console.log(evalVar); // 2. should be defined now
  …

}, evalVar); // 1. pass variable as an argument

您可以通过向 page.evaluate() 传递更多参数来传入多个变量:

You can pass in multiple variables by passing more arguments to page.evaluate():

await page.evaluate((a, b c) => { console.log(a, b, c) }, a, b, c)

参数必须可序列化为 JSON 或 JSHandles 的浏览器对象:https://pptr.dev/#?show=api-pageevaluatepagefunction-args

The arguments must either be serializable as JSON or JSHandles of in-browser objects: https://pptr.dev/#?show=api-pageevaluatepagefunction-args

这篇关于如何将变量传递给评估函数?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！