[Home](./index.md) > [puppeteer](./puppeteer.md) > [Frame](./puppeteer.frame.md) > [waitForFunction](./puppeteer.frame.waitforfunction.md)
## Frame.waitForFunction() method
Signature:
```typescript
waitForFunction(pageFunction: Function | string, options?: FrameWaitForFunctionOptions, ...args: SerializableOrJSHandle[]): Promise;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| pageFunction | Function \| string | the function to evaluate in the frame context. |
| options | [FrameWaitForFunctionOptions](./puppeteer.framewaitforfunctionoptions.md) | options to configure the polling method and timeout. |
| args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)\[\] | arguments to pass to the pageFunction. |
Returns:
Promise<[JSHandle](./puppeteer.jshandle.md)>
the promise which resolve when the `pageFunction` returns a truthy value.
## Remarks
## Example
The `waitForFunction` can be used to observe viewport size change:
```js
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:
```js
const selector = '.foo';
await frame.waitForFunction(
selector => !!document.querySelector(selector),
{}, // empty options object
selector
);
```