puppeteer/new-docs/puppeteer.frame.waitforfunction.md

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Frame.waitForFunction() method

Signature:

waitForFunction(pageFunction: Function | string, options?: FrameWaitForFunctionOptions, ...args: SerializableOrJSHandle[]): Promise<JSHandle>;

Parameters

Parameter	Type	Description
pageFunction	Function | string	the function to evaluate in the frame context.
options	FrameWaitForFunctionOptions	options to configure the polling method and timeout.
args	SerializableOrJSHandle[]	arguments to pass to the pageFunction.

Returns:

Promise<JSHandle>

the promise which resolve when the pageFunction returns a truthy value.

Remarks

Example

The waitForFunction can be used to observe viewport size change:

const puppeteer = require('puppeteer');

(async () => {
.  const browser = await puppeteer.launch();
.  const page = await browser.newPage();
.  const watchDog = page.mainFrame().waitForFunction('window.innerWidth < 100');
.  page.setViewport({width: 50, height: 50});
.  await watchDog;
.  await browser.close();
})();

To pass arguments from Node.js to the predicate of page.waitForFunction function:

const selector = '.foo';
await frame.waitForFunction(
  selector => !!document.querySelector(selector),
  {}, // empty options object
  selector
);