Page.evaluate() method

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

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

Signature:

class Page {
  evaluate<
    Params extends unknown[],
    Func extends EvaluateFunc<Params> = EvaluateFunc<Params>
  >(
    pageFunction: Func | string,
    ...args: Params
  ): Promise<Awaited<ReturnType<Func>>>;
}

Parameters

Parameter	Type	Description
pageFunction	Func | string	a function that is run within the page
args	Params	arguments to be passed to the pageFunction

Returns:

Promise<Awaited<ReturnType<Func>>>

the return value of pageFunction.

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(() => 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();