I am attempting to extract information using Puppeteer, but I’ve encountered an issue where the querySelector returns null for specific websites. Despite reviewing various suggestions on forums, I haven’t found a solution that works. Below is my code example along with a link that seems to fail:
const puppeteer = require('puppeteer');
(async () => {
const browserInstance = await puppeteer.launch();
const newPage = await browserInstance.newPage();
await newPage.goto('https://www.example.com/product/item-id');
const priceText = await newPage.evaluate(() => {
return document.querySelector('.item-price');
});
console.log(priceText);
browserInstance.close();
})();
Ensure the page has fully loaded before running the query. Add a delay or wait for specific elements:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://www.example.com/product/item-id', { waitUntil: 'domcontentloaded' });
await page.waitForSelector('.item-price');
const priceText = await page.evaluate(() => {
const element = document.querySelector('.item-price');
return element ? element.textContent : null;
});
console.log(priceText);
await browser.close();
})();
This waits for ‘.item-price’ to be available.
Hi DancingBird,
Another common reason for querySelector returning null is that the page might have dynamic content loading via JavaScript, which means that waitUntil: 'domcontentloaded' might not be sufficient. Here's how you can address this using Puppeteer:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
// Visit the target URL and ensure the network is idle
await page.goto('https://www.example.com/product/item-id', { waitUntil: 'networkidle2' });
// Wait explicitly for the element
await page.waitForSelector('.item-price', { timeout: 5000 });
const priceText = await page.evaluate(() => {
const element = document.querySelector('.item-price');
return element ? element.textContent.trim() : null;
});
console.log(priceText);
await browser.close();
})();
In this code, { waitUntil: 'networkidle2' } waits until there are no network connections for at least 500 ms. I also added a timeout to waitForSelector to ensure it doesn't hang indefinitely if the element is missing. This approach helps tackle pages with asynchronous content loading, providing a more reliable extraction process.
Another potential reason why querySelector could return null is due to the way the page manages its elements through iframes. Sometimes specific elements are loaded within iframes, and unless you target those iframes directly, you may not be able to access the elements using the standard DOM methods.
To handle this, you can modify your Puppeteer code to first identify and navigate into the relevant iframe before trying to select the desired element:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://www.example.com/product/item-id', { waitUntil: 'networkidle2' });
// Assume the target element resides within an iframe
const frameHandle = await page.$('iframe');
const frame = await frameHandle.contentFrame();
await frame.waitForSelector('.item-price', { timeout: 5000 });
const priceText = await frame.evaluate(() => {
const element = document.querySelector('.item-price');
return element ? element.textContent.trim() : null;
});
console.log(priceText);
await browser.close();
})();
This script accesses the iframe, waits for the .item-price class inside it, and retrieves the text content. This can be particularly useful on pages where major content is loaded into iframes, rather than directly in the parent document.
Hey DancingBird,
When querySelector returns null, the page might not fully load, or the element could be within an iframe. Here's a solution for iframes:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://www.example.com/product/item-id', { waitUntil: 'networkidle2' });
const frame = await page.frames().find(frame => frame.url().includes('iframe-part')); // Adjust as needed
await frame.waitForSelector('.item-price');
const priceText = await frame.evaluate(() => {
const element = document.querySelector('.item-price');
return element ? element.textContent.trim() : null;
});
console.log(priceText);
await browser.close();
})();
This ensures you're targeting elements inside iframes. Check iframes by examining the page sources for better targeting. Hope this helps!