如何将变量传递给评估函数?

本文介绍了如何将变量传递给评估函数?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在尝试将一个变量传递给 page.evaluate() 函数api.md#pageevaluatepagefunction-args" rel="noreferrer">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('www.google.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:pptr.dev/#?show=api-pageevaluatepagefunction-args

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