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Use and await Puppeteer’s page.waitForFunction() with a predicate that becomes truthy in the page context:
await page.waitForFunction(() => window.appReady === true);The wait resolves when the predicate returns any truthy value, not just the Boolean true. Awaiting it prevents the next Node.js step from running before the page condition is met.
Use waitForFunction for a page-side condition
page.waitForFunction() repeatedly evaluates a function in the browser page and resolves when its result is truthy. It is useful for conditions that are not simply selecting or interacting with one element, such as an application flag becoming ready.
await page.waitForFunction(() => window.appReady === true);
// Code here runs after the condition succeeds.The predicate runs in the page context, so it can read page globals and browser APIs. It does not automatically have access to variables defined only in your Node.js script.
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Pass values into the predicate
Provide the options object as the second argument, then pass any predicate arguments after it. Those values become parameters to the function running in the page.
const selector = '.foo';
await page.waitForFunction(
selector => Boolean(document.querySelector(selector)),
{}, // options
selector, // argument passed into the page-context function
);This example waits until an element matching .foo exists. The empty object occupies the options position; the selector follows it as an argument.
Set a timeout, polling mode, or cancellation
The documented default timeout is 30,000 milliseconds. Set timeout in the options object to choose another limit, or use timeout: 0 to disable the timeout. You can also change Puppeteer’s default timeout with Page.setDefaultTimeout(). An AbortSignal can cancel a wait. See the waitForFunction options for the API details.
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await page.waitForFunction(
() => window.appReady === true,
{ timeout: 10_000, polling: 100 },
);This example stops waiting after 10 seconds if the condition has not succeeded and checks at 100-millisecond intervals. If the timeout expires, the wait rejects rather than allowing subsequent code to proceed as if the condition succeeded.
Choose polling based on what changes the condition
raf(the default) reevaluates on animation frames. The API describes it as the tightest polling mode and suitable for observing styling changes.mutationreevaluates when the DOM changes. Use it when a DOM mutation can make the predicate true.- A number sets an interval in milliseconds. Use a numeric interval for conditions that need periodic checks rather than DOM-mutation or animation-frame checks.
Polling controls how often Puppeteer reevaluates the condition; it does not make an unrelated condition become true. Select the mode based on the event that can change the predicate.
Use a locator when the condition is about an element
Puppeteer’s interaction guide recommends locators for selecting and interacting with elements. Locators automatically wait for element state, and they can also use a function-based condition—for example, waiting until at least three paragraphs exist and returning their text. See the page interactions guide.
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Use a locator when the task is element selection, interaction, or readiness that a locator can express. Use waitForFunction when you need an arbitrary page-side predicate that is not better represented by a locator.
Common problems and fixes
The wait never completes
Check that the predicate can actually become truthy in the page context. Confirm the property or selector exists on the page, and verify that the code changing it runs in the same page you are waiting on. A selector argument must come after the options object.
The wait times out
A timeout means the predicate did not return a truthy value before the configured limit. Check the condition and its timing; then increase the timeout only if the page legitimately needs longer. Use timeout: 0 only when an unbounded wait is intentional, or use an AbortSignal when the caller should control cancellation.
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The next step runs too early
Await the returned promise. Without await, later code can continue before Puppeteer observes a truthy result.
Polling does not match the page behavior
Use mutation for a condition driven by DOM changes, raf for changes such as styling that should be observed across frames, or a numeric interval for periodic checks of other state.
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Version note
The official API reference result for Page.waitForFunction and the interaction guide identify Puppeteer version 25.12.0, while the options reference result displayed version 25.3.0. Check the documentation for the version installed in your project before relying on version-specific details.
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