puppeteer/website/versioned_docs/version-9.1.1/puppeteer.page.evaluate.md

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Page.evaluate() method

Signature:

evaluate<T extends EvaluateFn>(pageFunction: T, ...args: SerializableOrJSHandle[]): Promise<UnwrapPromiseLike<EvaluateFnReturnType<T>>>;

Parameters

Parameter	Type	Description
pageFunction	T	a function that is run within the page
args	SerializableOrJSHandle[]	arguments to be passed to the pageFunction

Returns:

Promise<UnwrapPromiseLike<EvaluateFnReturnType<T>>>

the return value of pageFunction.

Remarks

Evaluates a function in the page's context and returns the result.

If the function passed to page.evaluteHandle returns a Promise, the function will wait for the promise to resolve and return its value.

Example 1

const result = await frame.evaluate(() => {
  return Promise.resolve(8 * 7);
});
console.log(result); // prints "56"

You can pass a string instead of a function (although functions are recommended as they are easier to debug and use with TypeScript):

Example 2

const aHandle = await page.evaluate('1 + 2');

To get the best TypeScript experience, you should pass in as the generic the type of pageFunction:

const aHandle = await page.evaluate<() => number>(() => 2);

Example 3

ElementHandle instances (including JSHandles) can be passed as arguments to the pageFunction:

const bodyHandle = await page.$('body');
const html = await page.evaluate(body => body.innerHTML, bodyHandle);
await bodyHandle.dispose();