错误:评估失败:ReferenceError:未定义util

时间:2018-03-22 13:04:59

标签: javascript node.js puppeteer

我试图将util模块对象传递给puppeteer page.evaluate但没有成功。我理解在How to pass required module object to puppeteer page.evaluate 中提出了这个问题,但提供的解决方案在我的案例中不起作用。 MWE:

const puppeteer = require("puppeteer");

const path = "http://books.toscrape.com/";

// scrape funs 
(async () =>{
    const browser = await puppeteer.launch({headless: false});
    const page = await browser.newPage();
    await page.goto(path, {waitUntil: "networkidle2", timeout: 0});
    await page.waitFor(1000);
    await page.addScriptTag({path: './node_modules/util/util.js'});
    // selector with replaceable element
    const buttonText = await page.evaluate(() => {
        let selectorButton = "#default > div > div > div > div > section > div:nth-child(2) > ol > li:nth-child(%s) > article > div.product_price > form > button";
        let buttons = [];
        for(let i = 1; i < 21; i ++){
            let textOut = document.querySelector(util.format(selectorButton, i)).innerText;
            buttons.push(textOut);
        };
        return buttons;  
    });

// return
await browse.close();
console.log(buttonText);
})();

显示错误:

  

UnhandledPromiseRejectionWarning:未处理的承诺拒绝(拒绝ID:1):错误:评估失败:ReferenceError:util未定义

谢谢

编辑1

在初始行中添加const util = require("util");并且无法正常工作,如How to pass required module object to puppeteer page.evaluate所示。

编辑2

即使我使用browserify,我似乎无法将util模块注入puppeteer页面。步骤进行:

在项目PATH上,按如下方式创建main.jsvar util = require('util');

然后在终端PATHbrowserify main.js -o bundle.js。项目bundle.js中会显示PATH个文件。

然后运行以下命令:

const puppeteer = require("puppeteer");
const path = "http://books.toscrape.com/";

// scrape funs 
(async () =>{
    const browser = await puppeteer.launch({headless: false});
    const page = await browser.newPage();
    await page.goto(path, {waitUntil: "networkidle2", timeout: 0});
    await page.waitFor(1000);
    await page.addScriptTag({path: "main.js"});
    await page.addScriptTag({path: "bundle.js"});
    // selector with replaceable element
    const buttonText = await page.evaluate(() => {
        let buttons = [];
        let selectorButton = "#default > div > div > div > div > section > div:nth-child(2) > ol > li:nth-child(%s) > article > div.product_price > form > button";
        for(let i = 1; i < 21; i ++){
            let textOut = document.querySelector(util.format(selectorButton, i)).innerText;
            buttons.push(textOut);
        };
        return buttons;  
    });

// return
await browse.close();
console.log(buttonText);
})();

错误:

  

UnhandledPromiseRejectionWarning:未处理的承诺拒绝(拒绝ID:1):错误:评估失败:TypeError:无法读取属性&#39;格式&#39;未定义的       at:5:55

1 个答案:

答案 0 :(得分:2)

您需要包含与./node_modules/util/util.js兼容的浏览器。您可以使用browserify执行此操作或使用其在线服务Browserify Wizard - util下载浏览器版本。

https://try-puppeteer.appspot.com/上的代码

const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto("http://books.toscrape.com/", {waitUntil: "networkidle2", timeout: 0});
await page.waitFor(1000);

//Copy of https://wzrd.in/standalone/util@latest
await page.addScriptTag({url: "https://cdn.rawgit.com/brahma-dev/099d0d6d43a5d013603bcd245ee7a862/raw/b0c6bb82905b5b868c287392000dc2487c41994d/util.js"});

// selector with replaceable element
const buttonText = await page.evaluate(() => {
    let buttons = [];
    let selectorButton = "#default > div > div > div > div > section > div:nth-child(2) > ol > li:nth-child(%s) > article > div.product_price > form > button";
    for(let i = 1; i < 21; i ++){
        let textOut = document.querySelector(util.format(selectorButton, i)).innerText;
        buttons.push(textOut);
    };
    return buttons;  
});

// return
await browser.close();
console.log(buttonText);