Method: Playwright::Page#wait_for_function

Defined in:

lib/playwright_api/page.rb

#wait_for_function(expression, arg: nil, polling: nil, timeout: nil) ⇒ Object

Returns when the ‘expression` returns a truthy value. It resolves to a JSHandle of the truthy value.

The [‘method: Page.waitForFunction`] can be used to observe viewport size change:

“‘js const { webkit } = require(’playwright’); // Or ‘chromium’ or ‘firefox’.

(async () =>

const browser = await webkit.launch();
const page = await browser.newPage();
const watchDog = page.waitForFunction(() => window.innerWidth < 100);
await page.setViewportSize({width: 50, height: 50);
await watchDog;
await browser.close();

})(); “‘

“‘python async import asyncio from playwright.async_api import async_playwright

async def run(playwright):

webkit = playwright.webkit
browser = await webkit.launch()
page = await browser.new_page()
await page.evaluate("window.x = 0; setTimeout(() => { window.x = 100 }, 1000);")
await page.wait_for_function("() => window.x > 0")
await browser.close()

async def main():

async with async_playwright() as playwright:
    await run(playwright)

asyncio.run(main()) “‘

“‘python sync from playwright.sync_api import sync_playwright

def run(playwright):

webkit = playwright.webkit
browser = webkit.launch()
page = browser.new_page()
page.evaluate("window.x = 0; setTimeout(() => { window.x = 100 }, 1000);")
page.wait_for_function("() => window.x > 0")
browser.close()

with sync_playwright() as playwright:

run(playwright)

“‘

To pass an argument to the predicate of [‘method: Page.waitForFunction`] function:

“‘js const selector = ’.foo’; await page.waitForFunction(selector => !!document.querySelector(selector), selector); “‘

“‘python async selector = “.foo” await page.wait_for_function(“selector => !!document.querySelector(selector)”, selector) “`

“‘python sync selector = “.foo” page.wait_for_function(“selector => !!document.querySelector(selector)”, selector) “`

Shortcut for main frame’s [‘method: Frame.waitForFunction`].

# File 'lib/playwright_api/page.rb', line 1606

def wait_for_function(expression, arg: nil, polling: nil, timeout: nil)
  wrap_impl(@impl.wait_for_function(unwrap_impl(expression), arg: unwrap_impl(arg), polling: unwrap_impl(polling), timeout: unwrap_impl(timeout)))
end