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Puppeteer log inside page.evaluate

How can I console.log something inside the page.evaluate, passing it to node and using it during the evaluation of the page?

I actually want to log the progress of the page.evaluate to the console and show some results to the user.

like image 221
Alex Arvanitidis Avatar asked Sep 13 '17 13:09

Alex Arvanitidis


10 Answers

Update for puppeteer 12, adapted from the current documentation:

page.on('console', async (msg) => {
  const msgArgs = msg.args();
  for (let i = 0; i < msgArgs.length; ++i) {
    console.log(await msgArgs[i].jsonValue());
  }
});

await page.evaluate(() => console.log('hello', 5));
await page.evaluate(() => console.log({ foo: 'bar' }));
await page.evaluate(() => console.log([1, 2, 3, 4, 5]));

Shows the following results:

hello  
5  
{ foo: 'bar' }  
[ 1, 2, 3, 4, 5 ]  
like image 103
Vaviloff Avatar answered Oct 02 '22 11:10

Vaviloff


The easiest way to get it to work exactly like you'd expect

const page = await browser.newPage();
page.on('console', (log) => console[log._type](log._text));
like image 24
Clay Risser Avatar answered Oct 02 '22 11:10

Clay Risser


A lot of the answers provided previously no longer work today. Also one thing that can be very annoying on some pages, is the "warning" messages which pollutes the output. One way to fix that is to filter for the type of the message. The following code helps reduce the noise and works with current versions of Puppeteer:

const browser = await puppeteer.launch();
const page = await browser.newPage();
page.on('console', consoleMessageObject => function (consoleMessageObject) {
    if (consoleMessageObject._type !== 'warning') {
        console.debug(consoleMessageObject._text)
    }
});

await page.goto('https://google.com');
const result = await page.evaluate(() => {
    console.log('Browser scope.');
    return 'Normal scope.';
});
console.log(result)
like image 43
Nicolas Bouvrette Avatar answered Oct 02 '22 11:10

Nicolas Bouvrette


Update for version 1.15.x and above - Jan 2020

In the latest version args has been replaced with _args.

So when you are using page.evaluate() or page.evaluateHandle() and you want to get the console.log() text from the browser context back to node, use the following code and make sure to set the listener before any console.log() calls:

Code:

    // First we register our listener.
    page.on('console', msg => {
    for (let i = 0; i < msg._args.length; ++i)
        console.log(`${i}: ${msg._args[i]}`);
    });

    // Then we call the log.
    page.evaluate(() => console.log('Hello World'));

Explanation:

You can't see the console.log() text in your node console or set node breakpoints inside page.evaluate() or page.evaluateHandle(), because the code inside those functions is running only in the browser context. If you would launch puppeteer in none headless mode you would see the console.log() message showing in the browser.

Sidenote:

In most cases you don't really need to log inside the browser context and you can do the same work in the 'Console' tab of your browser 'Developer tools' section.

like image 34
raphaeli Avatar answered Oct 02 '22 11:10

raphaeli


I like @Vaviloff's answer, but you will log the whole ConsoleMessage object when you may just want the text. Thus, I personally use the below:

const EOL = require('os').EOL;
const _page = await browser.newPage();

_page.on('console', _fCleanLog);

function _fCleanLog(ConsoleMessage) {
    console.log(ConsoleMessage.text + EOL);
}
like image 43
John Vandivier Avatar answered Oct 02 '22 11:10

John Vandivier


Implement the notifyUi function in this code sample:

const page = await browser.newPage();
page.on('console', (...args) => {
    this.notifyUi('[chrome] ' + args[0]);
});
await page.goto(url);
const result = await page.evaluate(() => {
    console.log('I am alive');
    return Promise.resolve(true);
});
this.notifyUi('Evaluation returned with ' + result);
like image 25
Paul Avatar answered Oct 02 '22 11:10

Paul


const page = await browser.newPage();
page.on("console", msg => {
for (let i = 0; i < msg.args().length; ++i)
console.log(`${i}: ${msg.args()[i]}`);
});

try this one if none of the above works. shows no error logs but only the log I created.

like image 45
Hyung Doe Avatar answered Oct 02 '22 12:10

Hyung Doe


I am trying to share my workaround if it helps anybody in future.

  1. Print all the console outputs to stdout including warning, error, log:

    page = await browser.newPage();
    page.on("console", (consoleObj) => console.log(consoleObj.text()));
    
  2. Print everything except warning:

    page.on('console', consoleObj => {
        if (consoleObj.type() !== 'warning') {
            console.log(consoleObj.text());
        }
    })
    
  3. Print only logs (Ex: console.logs).

    page.on('console', consoleObj => {
        if (consoleObj.type() === 'log') {
            console.log(consoleObj.text());
        }
    })
    

The last one helped me more to debug efficiently.

like image 39
Abdullah Al Maruf - Tuhin Avatar answered Oct 02 '22 11:10

Abdullah Al Maruf - Tuhin


I share this solution for future readers who would more like to know how to get the returned value of an evaluation instead.

const element = await page.$("a selector");
const text = await page.evaluate(element => element.textContent);
like image 25
Changdae Park Avatar answered Oct 02 '22 11:10

Changdae Park


await page.evaluate(()=>{
      var string = 'I want to print this';
      return string;
}).then(console.log);
        
like image 30
Tomas G. Avatar answered Oct 02 '22 10:10

Tomas G.