Version: 1.0.0

Scraping and verification

Contents#


Evaluating JavaScript#

Execute JavaScript function in the page:

const href = await page.evaluate(() => document.location.href);

If the result is a Promise or if the function is asynchronous evaluate will automatically wait until it's resolved:

const status = await page.evaluate(async () => {
const response = await fetch(location.href);
return response.status;
});

Get object handle and use it in multiple evaluations:

// Create a new array in the page, write a reference to it in
// window.myArray and get a handle to it.
const myArrayHandle = await page.evaluateHandle(() => {
window.myArray = [1];
return myArray;
});
// Get current length of the array using the handle.
const length = await page.evaluate(
(arg) => arg.myArray.length,
{ myArray: myArrayHandle }
);
// Add one more element to the array using the handle
await page.evaluate((arg) => arg.myArray.push(arg.newElement), {
myArray: myArrayHandle,
newElement: 2
});
// Get current length of the array using window.myArray reference.
const newLength = await page.evaluate(() => window.myArray.length);
// Release the object when it's no longer needed.
await myArrayHandle.dispose();

API reference#


Capturing screenshot#

// Save to file
await page.screenshot({path: 'screenshot.png'});
// Capture full page
await page.screenshot({path: 'screenshot.png', fullPage: true});
// Capture into buffer
const buffer = await page.screenshot();
console.log(buffer.toString('base64'));
// Capture given element
const elementHandle = await page.$('.header');
await elementHandle.screenshot({ path: 'screenshot.png' });

API reference#


Page events#

You can listen for various events on the page object. Following are just some of the examples of the events you can assert and handle:

"console" - get all console messages from the page#

page.on('console', msg => {
// Handle only errors.
if (msg.type() !== 'error')
return;
console.log(`text: "${msg.text()}"`);
});

"dialog" - handle alert, confirm, prompt#

page.on('dialog', dialog => {
dialog.accept();
});

"popup" - handle popup windows#

const [popup] = await Promise.all([
page.waitForEvent('popup'),
page.click('#open')
]);

API reference#


Handling exceptions#

Listen uncaught exceptions in the page:

// Log all uncaught errors to the terminal
page.on('pageerror', exception => {
console.log(`Uncaught exception: "${exception}"`);
});
// Navigate to a page with an exception.
await page.goto('data:text/html,<script>throw new Error("Test")</script>');

API reference#