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What waitForFunction() does
Puppeteer’s API reference describes the method as waiting for a supplied function to return a truthy value when evaluated in the page context. The method returns a promise for a handle to the value returned by the function. See the Puppeteer Page.waitForFunction API.
Use it when readiness depends on a page condition rather than simply the presence of an element. For example, a page may need to reach a particular viewport width, expose a JavaScript value, or finish an application-specific state change before your script continues.
Options at a glance
| Option | Documented default or values | What it controls |
|---|---|---|
polling |
'raf' by default; 'mutation'; or a number of milliseconds |
When Puppeteer reevaluates the condition. |
timeout |
30000 milliseconds by default; 0 disables the timeout |
The maximum duration of the wait. The default can also be changed with Page.setDefaultTimeout(). |
signal |
Optional AbortSignal |
Lets your code cancel a pending wait. |
These values are documented in Puppeteer’s FrameWaitForFunctionOptions reference, identified as version 25.3.0. The Page method reference is identified as version 25.12.0; check the documentation matching the version installed in your project.
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How to choose a polling option
'raf': check on animation frames
This is the documented default. Puppeteer evaluates the function in requestAnimationFrame callbacks. The API describes it as the tightest polling mode and says it is suitable for observing styling changes. It is a natural fit for conditions that may change as the page renders, such as a computed style or viewport-related state.
'mutation': check on DOM changes
With 'mutation', Puppeteer evaluates the condition on DOM mutations. Consider it when the condition is driven by DOM updates, such as an element being inserted or its contents changing. It is not a universal speed improvement; the documentation does not provide comparative performance measurements.
A number: check at a fixed interval
Pass a number of milliseconds to evaluate the predicate at that interval. Use this when a fixed checking cadence is appropriate for the condition. The API documentation does not establish a best interval or show that a particular interval is faster than the others.
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Set the timeout and cancel waits
Timeout behavior
The default timeout is 30,000 milliseconds. Set timeout in the options object for a wait-specific limit, or configure the Page default with Page.setDefaultTimeout(). A timeout of 0 disables this time limit. If you disable it, make sure another part of your task can end or cancel a wait that never becomes true.
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Cancellation with an AbortSignal
Pass an AbortSignal as signal when the surrounding operation may need to stop a pending wait—for example, when a task is cancelled or no longer needs the result. Cancellation is distinct from a timeout: it is triggered by your code’s signal rather than by the wait exceeding its time limit.
Pass arguments to the page function
The signature is page.waitForFunction(pageFunction, options?, ...args). The options object occupies the second position; values passed to the page function follow it. Include an empty object when you have function arguments but no options to set:
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const selector = '.foo';
await page.waitForFunction(
selector => Boolean(document.querySelector(selector)),
{},
selector,
);Without the second-position options object, the selector would occupy the options position instead of being passed as the predicate’s argument.
Complete examples
Wait for a selector
await page.waitForFunction(
selector => Boolean(document.querySelector(selector)),
{ polling: 'mutation', timeout: 10_000 },
'.results-ready',
);This example checks in response to DOM mutations and gives the condition up to 10 seconds. Choose the polling mode based on what changes the condition; the timeout is an example limit, not a recommended value for every page.
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Wait for a viewport condition
await page.waitForFunction(() => window.innerWidth < 100);The API reference uses this type of condition to demonstrate waiting for a viewport width before changing the viewport. With no options supplied, the documented default polling and timeout apply.
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Use an asynchronous predicate
The page function can be asynchronous. Puppeteer’s API example fetches data in the page, updates it with an image, waits three seconds, and removes the image. That example demonstrates asynchronous predicates; it is not a performance recommendation. Ensure the asynchronous work can complete and that your timeout or cancellation policy matches the task.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common failures and fixes
- The wait times out: The condition did not become truthy before the timeout. Check that the page actually reaches the expected state, that the predicate tests the right thing, and that the timeout is appropriate for the operation.
- The call receives the wrong argument: The options object is the second argument. Put function arguments after it, using
{}when no options are needed. - The wait never ends: A timeout of
0disables the time limit. Use a finite timeout or arrange cancellation through anAbortSignal. - The predicate misses a change or checks too often for the condition: Match polling to the trigger: animation-frame callbacks for render-related changes, DOM mutations for DOM-driven changes, or a numeric interval for fixed-cadence checks. The docs do not establish one mode as best for every page.
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Frequently Asked Questions
Can the function passed to waitForFunction() be asynchronous?
Yes. Puppeteer supports an asynchronous page function; its API example performs a fetch and updates the page before the wait resolves.
What does waitForFunction() return?
It returns a promise for a handle corresponding to the awaited return type of the supplied page function.
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