puppeteer/docs/api/puppeteer.page.exposefunction.md
Alex Rudenko 1668d47b2f
docs: various doc improvements (#9396)
See commits for details.

Closes #1837, #5880, #7822, #8101, #8821, #9367, #9382, #9378, #4731
2022-12-09 13:57:39 +01:00

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sidebar_label
Page.exposeFunction

Page.exposeFunction() method

The method adds a function called name on the page's window object. When called, the function executes puppeteerFunction in node.js and returns a Promise which resolves to the return value of puppeteerFunction.

If the puppeteerFunction returns a Promise, it will be awaited.

:::note

Functions installed via page.exposeFunction survive navigations.

:::note

Signature:

class Page {
  exposeFunction(
    name: string,
    pptrFunction:
      | Function
      | {
          default: Function;
        }
  ): Promise<void>;
}

Parameters

Parameter Type Description
name string Name of the function on the window object
pptrFunction Function | { default: Function; } Callback function which will be called in Puppeteer's context.

Returns:

Promise<void>

Example 1

An example of adding an md5 function into the page:

import puppeteer from 'puppeteer';
import crypto from 'crypto';

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  page.on('console', msg => console.log(msg.text()));
  await page.exposeFunction('md5', text =>
    crypto.createHash('md5').update(text).digest('hex')
  );
  await page.evaluate(async () => {
    // use window.md5 to compute hashes
    const myString = 'PUPPETEER';
    const myHash = await window.md5(myString);
    console.log(`md5 of ${myString} is ${myHash}`);
  });
  await browser.close();
})();

Example 2

An example of adding a window.readfile function into the page:

import puppeteer from 'puppeteer';
import fs from 'fs';

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  page.on('console', msg => console.log(msg.text()));
  await page.exposeFunction('readfile', async filePath => {
    return new Promise((resolve, reject) => {
      fs.readFile(filePath, 'utf8', (err, text) => {
        if (err) reject(err);
        else resolve(text);
      });
    });
  });
  await page.evaluate(async () => {
    // use window.readfile to read contents of a file
    const content = await window.readfile('/etc/hosts');
    console.log(content);
  });
  await browser.close();
})();