Puppeteer js, unable to execute page in $$eval - puppeteer

I've seen this asked around but I can't pinpoint what I'm doing wrong.
Error: UnhandledPromiseRejectionWarning: Error: Evaluation failed: ReferenceError: page is not defined
const page = await browser.newPage();
await page.goto('https://example.com');
const getAllElements = await page.$$eval('.aclass', links => {
links.map(link => {
page.hover(link);
page.screenshot({path: `example${link}.png`});
})
})
Expected behavior is that I go to example.com, I then get all the .aclass elements. Return those as 'links" then I map over each link, which should give me each element in link. I then am expecting to be able to page.hover and page.screenshot. However this is where I get the error that page is not defined. Any idea what I'm doing wrong?

hover and screenshot returns Promise.
Don't pass page to page.$$eval. Instead you can do the following:
const page = await browser.newPage();
await page.goto('https://example.com');
const getAllElements = await page.$$('.aclass');
for (let [i, link] of getAllElements.entries()) {
await link.hover();
await link.screenshot({path: `example${i}.png`});
}

Related

Using puppeteer get a selector from an input label

So, I have a front end in React.js or Ember.js - not sure. I'm just trying to automate some testing for it. When looking at the HTML in the Chrome Dev Tools, I see
<label class="MuiFormLabel-root-16 MuiInputLabel-root-5 MuiInputLabel-formControl-10 MuiInputLabel-animated-13 MuiInputLabel-outlined-15" data-shrink="false">Username</label>
This is set in an iframe (which isn't too important for this issue). I'm trying to get the ElementHandler using the puppeteer function
frame.$(selector)
How do I get the selector given
Username
I've tried a few things, but with little success.
If I understand correctly, you need to find an element by its text content. If so, these are at least two ways:
const puppeteer = require('puppeteer');
(async function main() {
try {
const browser = await puppeteer.launch(); // { headless: false, defaultViewport: null, args: ['--lang=en'] }
const [page] = await browser.pages();
await page.goto('https://example.org/');
const element1 = await page.evaluateHandle(() => {
return [...document.querySelectorAll('h1')].find(h1 => h1.innerText === 'Example Domain');
});
console.log(await (await element1.getProperty('outerHTML')).jsonValue());
const [element2] = await page.$x('//h1[text()="Example Domain"]');
console.log(await (await element2.getProperty('outerHTML')).jsonValue());
await browser.close();
} catch (err) {
console.error(err);
}
})();
My solution was to place HTML data attributes in the front end code so that I can easily select them.

Puppeteer page.evaluate not working as expected

Can someone explain why this code isn't working. I have a console log before I run page.evaluate() which logs what I expect, but the console log inside page.evaluate never runs.
const puppeteer = require('puppeteer');
(async () => {
try {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://www.example.com');
page.on('response', async response => {
const url = response.url();
if (url.includes('something')) {
console.log('this code runs');
await page.evaluate(() => {
console.log("this code doesn't run");
});
}
});
} catch (err) {
console.log(err);
}
})();
Console log doesn't work in page.evaluate()
https://github.com/GoogleChrome/puppeteer/issues/1944
Try to use this code for display console.log from evaluate
page.on('console', msg => {
for (let i = 0; i < msg.args().length; ++i)
console.log(`${i}: ${msg.args()[i]}`);
});
page.evaluate(() => console.log('hello', 5, {foo: 'bar'}));
https://pptr.dev/#?product=Puppeteer&version=v1.20.0&show=api-event-console
The code inside page.evaluate is run in the browser context, so the console.log works, but inside the Chrome console and not the Puppeteer one.
To display the logs of the Chrome context inside the Puppeteer console, you can set dumpio to true in the arguments when launching a browser using Puppeteer:
const browser = await puppeteer.launch({
dumpio: true
})
Console.log works but in the browser context. I'm guessing here that you are trying to see the log in the CLI. If you want to see the log set headless to false and then see the log in the browser console.

How to invoke Chrome Node Screenshot from the console?

I know you can capture a single html node vial the command prompt, but is it possible to do this programmatically from the console similar to Puppeteer? I'd like to loop all elements on a page and capture them for occasional one-off projects where I don't want to set up a full auth process in puppeteer.
I'm referring to this functionality:
But executed from the console like during a foreach or something like that.
See the puppeteer reference here.
Something to the effect of this:
$x("//*[contains(#class, 'special-class-name')]").forEach((el)=> el.screenshot())
I just made a script that take a screenshot every submit button in Google main page. Just take a look and take some inspiration from it.
const puppeteer = require('puppeteer')
;(async () => {
const browser = await puppeteer.launch({
headless:false,
defaultViewport:null,
devtools: true,
args: ['--window-size=1920,1170','--window-position=0,0']
})
const page = (await browser.pages())[0]
const open = await page.goto ( 'https://www.google.com' )
const submit = await page.$$('input[type="submit"]')
const length = submit.length
let num = 0
const shot = submit.forEach( async elemHandle => {
num++
await elemHandle.screenshot({
path : `${Date.now()}_${num}.png`
})
})
})()
You can use ElementHandle.screenshot() to take a screenshot of a specific element on the page. The ElementHandle can be obtained from Page.$(selector) or Page.$$(selector) if you want to return multiple results.
const browser = await puppeteer.launch({ headless: true });
const page = await browser.newPage();
await page.goto("https://stackoverflow.com/questions/50715164");
const userInfo = await page.$(".user-info");
await userInfo.screenshot({ path: "userInfo.png" });
The output image after executing the code:

Looping through links(stories) and taking screenshots

What I'm trying to do here is loop through Storybook stories so I can perform visual regression testing on them:
const puppeteer = require('puppeteer');
const { toMatchImageSnapshot } = require('jest-image-snapshot');
expect.extend({ toMatchImageSnapshot });
test('no visual regression for button', async () => {
const selector = 'a[href*="?selectedKind=Buttons&selectedStory="]';
const browser = await puppeteer.launch({headless:false, slowMo: 350});
const page = await browser.newPage();
await page.goto('http://localhost:8080');
const storyLinks = await page.evaluate(() => {
const stories = Array.from(document.querySelectorAll('a[href*="?selectedKind=Buttons&selectedStory="]'));
const links = stories.map(story => story.href);
return links;
});
await storyLinks.forEach( (storyLink) => {
page.goto(storyLink).then(async (res,rej) => {
const screen = await page.screenshot();
return await expect(screen).toMatchImageSnapshot();
});
});
await browser.close();
});
One problem is that I get this because of the await broswer.close() that isn't waiting for everything to finish:
Protocol error (Page.navigate): Target closed.
at Session._onClosed (../../node_modules/puppeteer/lib/Connection.js:209:23)
at Connection._onClose (../../node_modules/puppeteer/lib/Connection.js:116:15)
at Connection.dispose (../../node_modules/puppeteer/lib/Connection.js:121:10)
at Browser.close (../../node_modules/puppeteer/lib/Browser.js:60:22)
at Object.<anonymous>.test (__tests__/visual.spec.js:24:16)
at <anonymous>
This happens for each storyLink except the first.
If I comment out the await browser.close() line, the screenshots are being taken, but not in the expected wait. Instead of each story having one screenshot, the last story is being screenshotted for the amount of stories. For example, I've got 4 stories in total, but I will have 4 screenshots of the last story instead of one for each story.
I don't understand why this behaviour is happening. The storyLinks returned from the page.evaluate funtions are correct, but then everything breaks and I've got no idea why.
Any ideas?
forEach is not good for async-await. Use for..of instead,
for (let storyLink of storyLinks) {
await page.goto(storyLink)
const screen = await page.screenshot();
await expect(screen).toMatchImageSnapshot();
};

Chrome puppeteer Close page on error event

I want to close pages when puppeteer faces on any error , sometimes page the page that i try to load crashes and it doesnt call .close();
(async () => {
const page = await browser.newPage();
await page.setViewport({width: resWidth, height: resHeight});
await page.goto(d["entities"]["urls"][0]["expanded_url"], {timeout :90000});
await page.screenshot({path: './resimdata/'+d['id']+'.png' ,fullPage: true});
await page.close();
})();
There is an issue/PR on puppeteer repo regarding this which will be helpful in similar situation.
Related Issue link: https://github.com/GoogleChrome/puppeteer/issues/952
Meanwhile, you can try this little hack, if the PR is there on version 0.12+, we don't have to worry about the following code.
(async() => {
const browser = await puppeteer.launch({headless: false});
const page = await browser.newPage();
function handleClose(msg){
console.log(msg);
page.close();
browser.close();
process.exit(1);
}
process.on("uncaughtException", () => {
handleClose(`I crashed`);
});
process.on("unhandledRejection", () => {
handleClose(`I was rejected`);
});
await page.goto("chrome://crash");
})();
Which will output something like the following,
▶ node app/app.js
I was rejected