How to iterate async function in puppeteer with NodeJS

Question

I want to take a screenshot with puppeteer and it's working for one post. But I want to make it iterate.

If it's normal function I can just wrote the function name in the last side of the code so that it can iterate. But this is async function so I don't know how to iterate it.

const puppeteer = require('puppeteer');

let postNumber = 1;
let by;

(async () => {
    const browser = await puppeteer.launch({
        executablePath: 'C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe',
        userDataDir: 'C:\\Users\\{computerName}\\AppData\\Local\\Google\\Chrome\\User Data',
        headless: false
    }); // default is true
    const page = await browser.newPage();
    await page.goto(`https://band.us/band/{someNumbers}/post/${postNumber}`, {
        waitUntil: 'networkidle2'
    });
    let element = await page.$('.boardList');
    by = await page.evaluate(() => document.getElementsByClassName('text')[0].textContent);
    console.log(by);

    await element.screenshot({
        path: `./image/${postNumber}-${by}.png`
    });
    console.log(`SAVED : ${postNumber}-${by}.png`)
    postNumber++;
    await browser.close();
})();

After the function is finished, the postNumber variable should be increase by one. And then run the code again by new URLs.

Thomas Dondorf · Accepted Answer · 2019-03-31 16:10:20Z

5

As you want to run the code one iteration after another, a normal for (or while) loop can be used. async/await code works fine with these.

You can use a for in your case like this:

(async () => {
    const browser = await puppeteer.launch(/* ... */);
    const page = await browser.newPage();

    for (let postNumber = 1; postNumber < 10; postNumber++) {
        await page.goto(/* ... */);
        let element = await page.$('.boardList');
        // ...
    }

    await browser.close();
})();

answered Mar 31, 2019 at 16:10

Thomas Dondorf

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Comments

vsemozhebuty · Accepted Answer · 2019-03-31 16:10:45Z

You can use any appropriate loop, like while-loop:

'use strict';

const puppeteer = require('puppeteer');

(async () => {
    const browser = await puppeteer.launch({
        executablePath: 'C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe',
        userDataDir: 'C:\\Users\\{computerName}\\AppData\\Local\\Google\\Chrome\\User Data',
        headless: false
    }); // default is true
    const page = await browser.newPage();

    let postNumber = 1;
    while (postNumber <= 10) {
      await page.goto(`https://band.us/band/{someNumbers}/post/${postNumber}`, {
          waitUntil: 'networkidle2'
      });
      const element = await page.$('.boardList');
      const by = await page.evaluate(() => document.getElementsByClassName('text')[0].textContent);
      console.log(by);

      await element.screenshot({
          path: `./image/${postNumber}-${by}.png`
      });
      console.log(`SAVED : ${postNumber}-${by}.png`)
      postNumber++;
    }

    await browser.close();
})();

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